TagREADME.md

Table of Contents

• Array (107)
• DFS (95)
• DP (85)
• Hash Table (69)
• String (60)
• Tree (55)
• Binary Search (40)
• BFS (39)
• Math (38)
• Two Pointers (38)
• Divide and Conquer (35)
• Backtracking (32)
• Linked List (31)
• Stack (30)
• Sort (22)
• BST (22)
• Design (21)
• Sequence DP (21)
• PriorityQueue (19)
• Greedy (18)
• Bit Manipulation (17)
• Coordinate DP (17)
• Heap (16)
• Union Find (15)
• Enumeration (15)
• Binary Tree (13)
• Segment Tree (12)
• Memoization (12)
• Trie (11)
• Graph (11)
• Subarray (11)
• PreSum (10)
• Lint (9)
• MinHeap (9)
• Backpack DP (8)
• Status DP (7)
• Double Sequence DP (6)
• Sliding Window (6)
• Quick Sort (6)
• Partition DP (5)
• Sweep Line (5)
• Topological Sort (5)
• Expression Tree (5)
• Merge Sort (4)
• Game Theory (4)
• Combination (4)
• Interval DP (4)
• MaxHeap (4)
• Permutation (3)
• Binary Indexed Tree (3)
• Minimum Binary Tree (3)
• Basic Implementation (3)
• Queue (3)
• Partition (3)
• Sequence DFS (2)
• Double Recursive (2)
• TreeSet (2)
• Matrix DFS (2)
• MiniMax (2)
• Deque (2)
• Geometry (2)
• Priority Queue (1)
• HashHeap (1)
• Binary Search Tree (1)
• KMP (1)
• Brainteaser (1)
• Interval (1)
• Bitwise DP (1)
• Quick Select (1)
• Bucket Sort (1)
• Monotonous Stack (1)
• PreProduct (1)
• Reservior Sampling (1)
• TreeMap (1)
• Two Stacks (1)
• Tree DP (1)

Array (107)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Missing Ranges.java	Medium	Java	[Array]
1	Next Permutation.java	Medium	Java	[Array]
2	Product of Array Exclude Itself.java	Medium	Java	[Array]
3	Recover Rotated Sorted Array.java	Easy	Java	[Array]
4	Triangle Count.java	Medium	Java	[Array]
5	Array Partition I.java	Easy	Java	[Array]
6	1-bit and 2-bit Characters.java	Easy	Java	[Array]
7	Non-decreasing Array.java	Easy	Java	[Array]
8	Max Consecutive Ones.java	Easy	Java	[Array]
9	Find All Numbers Disappeared in an Array.java	Easy	Java	[Array]
10	Largest Number At Least Twice of Others.java	Easy	Java	[Array]
11	Toeplitz Matrix.java	Easy	Java	[Array]
12	Game of Life.java	Medium	Java	[Array]
13	First Missing Positive.java	Hard	Java	[Array]
14	Majority Element II.java	Medium	Java	[Array]
15	Merge Sorted Array II.java	Easy	Java	[Array]
16	Summary Ranges.java	Medium	Java	[Array]
17	Maximize Distance to Closest Person.java	Easy	Java	[Array]
18	The Spiral Matrix II.java	Medium	Java	[Array]
19	Subsets.java	Medium	Java	[Array, BFS, Backtracking, Bit Manipulation, DFS]
20	Subsets II.java	Medium	Java	[Array, BFS, Backtracking, DFS]
21	Word Ladder II.java	Hard	Java	[Array, BFS, Backtracking, DFS, Hash Table, String]
22	Max Sum of Rectangle No Larger Than K.java	Hard	Java	[Array, BST, Binary Search, DP, Queue, TreeSet]
23	K Empty Slots.java	Hard	Java	[Array, BST, TreeSet]
24	Combination Sum IV.java	Medium	Java	[Array, Backpack DP, DP]
25	Combination Sum.java	Medium	Java	[Array, Backtracking, Combination, DFS]
26	Combination Sum II.java	Medium	Java	[Array, Backtracking, Combination, DFS]
27	Combination Sum III.java	Medium	Java	[Array, Backtracking, Combination, DFS]
28	Word Search.java	Medium	Java	[Array, Backtracking, DFS]
29	Search in Rotated Sorted Array II.java	Medium	Java	[Array, Binary Search]
30	Find Peak Element.java	Medium	Java	[Array, Binary Search]
31	Find Minimum in Rotated Sorted Array.java	Medium	Java	[Array, Binary Search]
32	Find Minimum in Rotated Sorted Array II.java	Hard	Java	[Array, Binary Search]
33	Search a 2D Matrix.java	Medium	Java	[Array, Binary Search]
34	Search for a Range.java	Medium	Java	[Array, Binary Search]
35	Search in Rotated Sorted Array.java	Medium	Java	[Array, Binary Search]
36	Median of Two Sorted Arrays.java	Hard	Java	[Array, Binary Search, DFS, Divide and Conquer]
37	Maximum Average Subarray II.java	Review	Java	[Array, Binary Search, PreSum]
38	Minimum Size Subarray Sum.java	Medium	Java	[Array, Binary Search, Subarray, Two Pointers]
39	Subarray Sum II.java	Hard	Java	[Array, Binary Search, Two Pointers]
40	Two Sum II - Input array is sorted.java	Medium	Java	[Array, Binary Search, Two Pointers]
41	2 Sum II.java	Medium	Java	[Array, Binary Search, Two Pointers]
42	Find the Duplicate Number.java	Medium	Java	[Array, Binary Search, Two Pointers]
43	Majority Element.java	Easy	Java	[Array, Bit Manipulation, Divide and Conquer]
44	Missing Number.java	Easy	Java	[Array, Bit Manipulation, Math]
45	Triangles.java	Medium	Java	[Array, Coordinate DP, DFS, DP, Memoization]
46	Unique Paths II.java	Medium	Java	[Array, Coordinate DP, DP]
47	Unique Path.java	Medium	Java	[Array, Coordinate DP, DP]
48	Longest Continuous Increasing Subsequence.java	Easy	Java	[Array, Coordinate DP, DP]
49	Minimum Path Sum.java	Medium	Java	[Array, Coordinate DP, DP]
50	Longest Increasing Continuous subsequence.java	Easy	Java	[Array, Coordinate DP, DP]
51	Jump Game II.java	Hard	Java	[Array, Coordinate DP, DP, Greedy]
52	Longest Increasing Continuous subsequence II.java	Medium	Java	[Array, Coordinate DP, DP, Memoization]
53	Max Area of Island.java	Easy	Java	[Array, DFS]
54	Maximum Subarray.java	Easy	Java	[Array, DFS, DP, Divide and Conquer, PreSum, Sequence DP, Subarray]
55	Construct Binary Tree from Preorder and Inorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Hash Table, Tree]
56	Construct Binary Tree from Inorder and Postorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Tree]
57	Coins in a Line III.java	Hard	Java	[Array, DP, Game Theory, Interval DP, Memoization]
58	Coins in a Line II.java	Medium	Java	[Array, DP, Game Theory, Memoization, MiniMax]
59	Jump Game.java	Medium	Java	[Array, DP, Greedy]
60	Maximum Subarray II.java	Medium	Java	[Array, DP, Greedy, PreSum, Sequence DP, Subarray]
61	Best Time to Buy and Sell Stock II.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Status DP]
62	Best Time to Buy and Sell Stock with Transaction Fee.java	Medium	Java	[Array, DP, Greedy, Sequence DP, Status DP]
63	Minimum Subarray.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Subarray]
64	Maximal Rectangle.java	Hard	Java	[Array, DP, Hash Table, Stack]
65	Best Time to Buy and Sell Stock III.java	Hard	Java	[Array, DP, Sequence DP]
66	Best Time to Buy and Sell Stock.java	Easy	Java	[Array, DP, Sequence DP]
67	Maximum Product Subarray.java	Medium	Java	[Array, DP, Subarray]
68	Insert Delete GetRandom O(1).java	Medium	Java	[Array, Design, Hash Table]
69	Rotate Image.java	Medium	Java	[Array, Enumeration]
70	Spiral Matrix.java	Medium	Java	[Array, Enumeration]
71	Task Scheduler.java	Medium	Java	[Array, Enumeration, Greedy, PriorityQueue, Queue]
72	Max Points on a Line.java	Hard	Java	[Array, Geometry, Hash Table, Math]
73	Find the Celebrity.java	Medium	Java	[Array, Greedy]
74	Contains Duplicate.java	Easy	Java	[Array, Hash Table]
75	Contains Duplicate II.java	Easy	Java	[Array, Hash Table]
76	Two Sum.java	Easy	Java	[Array, Hash Table]
77	Anagrams.java	Medium	Java	[Array, Hash Table]
78	Submatrix Sum.java	Medium	Java	[Array, Hash Table, PreSum]
79	Subarray Sum.java	Easy	Java	[Array, Hash Table, PreSum, Subarray]
80	Subarray Sum Equals K.java	Medium	Java	[Array, Hash Table, PreSum, Subarray]
81	Longest Consecutive Sequence.java	Hard	Java	[Array, Hash Table, Union Find]
82	Number of Airplane in the sky.java	Medium	Java	[Array, Interval, PriorityQueue, Sort, Sweep Line]
83	Plus One.java	Easy	Java	[Array, Math]
84	Friends Of Appropriate Ages.java	Medium	Java	[Array, Math]
85	Largest Rectangle in Histogram.java	Hard	Java	[Array, Monotonous Stack, Stack]
86	Sort Colors.java	Medium	Java	[Array, Partition, Quick Sort, Sort, Two Pointers]
87	Product of Array Except Self.java	Medium	Java	[Array, PreProduct]
88	Insert Interval.java	Hard	Java	[Array, PriorityQueue, Sort]
89	Merge Intervals.java	Medium	Java	[Array, PriorityQueue, Sort, Sweep Line]
90	Median.java	Easy	Java	[Array, Quick Select, Quick Sort]
91	Partition Array.java	Medium	Java	[Array, Quick Sort, Sort, Two Pointers]
92	Wiggle Sort.java	Medium	Java	[Array, Sort]
93	The Smallest Difference.java	Medium	Java	[Array, Sort, Two Pointers]
94	Trapping Rain Water.java	Hard	Java	[Array, Stack, Two Pointers]
95	Unique Characters.java	Easy	Java	[Array, String]
96	Maximum Average Subarray I.java	Easy	Java	[Array, Subarray]
97	My Calendar I.java	Medium	Java	[Array, TreeMap]
98	Partition Array by Odd and Even.java	Easy	Java	[Array, Two Pointers]
99	3 Sum Closest.java	Medium	Java	[Array, Two Pointers]
100	3Sum.java	Medium	Java	[Array, Two Pointers]
101	3Sum Smaller.java	Medium	Java	[Array, Two Pointers]
102	Remove Duplicates from Sorted Array.java	Easy	Java	[Array, Two Pointers]
103	Remove Duplicates from Sorted Array II.java	Medium	Java	[Array, Two Pointers]
104	Container With Most Water.java	Medium	Java	[Array, Two Pointers]
105	Merge Sorted Array.java	Easy	Java	[Array, Two Pointers]
106	Move Zeroes.java	Easy	Java	[Array, Two Pointers]

DFS (95)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Subsets.java	Medium	Java	[Array, BFS, Backtracking, Bit Manipulation, DFS]
1	Subsets II.java	Medium	Java	[Array, BFS, Backtracking, DFS]
2	Word Ladder II.java	Hard	Java	[Array, BFS, Backtracking, DFS, Hash Table, String]
3	Combination Sum.java	Medium	Java	[Array, Backtracking, Combination, DFS]
4	Combination Sum II.java	Medium	Java	[Array, Backtracking, Combination, DFS]
5	Combination Sum III.java	Medium	Java	[Array, Backtracking, Combination, DFS]
6	Word Search.java	Medium	Java	[Array, Backtracking, DFS]
7	Median of Two Sorted Arrays.java	Hard	Java	[Array, Binary Search, DFS, Divide and Conquer]
8	Triangles.java	Medium	Java	[Array, Coordinate DP, DFS, DP, Memoization]
9	Max Area of Island.java	Easy	Java	[Array, DFS]
10	Maximum Subarray.java	Easy	Java	[Array, DFS, DP, Divide and Conquer, PreSum, Sequence DP, Subarray]
11	Construct Binary Tree from Preorder and Inorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Hash Table, Tree]
12	Construct Binary Tree from Inorder and Postorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Tree]
13	Course Schedule.java	Medium	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
14	Alien Dictionary.java	Hard	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
15	Nested List Weight Sum.java	Easy	Java	[BFS, DFS]
16	Find the Connected Component in the Undirected Graph.java	Medium	Java	[BFS, DFS]
17	Walls and Gates.java	Medium	Java	[BFS, DFS]
18	The Maze.java	Medium	Java	[BFS, DFS]
19	Remove Invalid Parentheses.java	Review	Java	[BFS, DFS, DP]
20	Serialize and Deserialize Binary Tree.java	Hard	Java	[BFS, DFS, Deque, Design, Divide and Conquer, Tree]
21	Clone Graph.java	Medium	Java	[BFS, DFS, Graph]
22	Course Schedule II.java	Medium	Java	[BFS, DFS, Graph, Topological Sort]
23	Redundant Connection.java	Medium	Java	[BFS, DFS, Graph, Tree, Union Find]
24	Evaluate Division.java	Medium	Java	[BFS, DFS, Graph, Union Find]
25	Number of Connected Components in an Undirected Graph.java	Medium	Java	[BFS, DFS, Graph, Union Find]
26	Graph Valid Tree.java	Medium	Java	[BFS, DFS, Graph, Union Find]
27	Binary Tree Vertical Order Traversal.java	Medium	Java	[BFS, DFS, Hash Table, Tree]
28	Number of Islands.java	Medium	Java	[BFS, DFS, Matrix DFS, Union Find]
29	Surrounded Regions.java	Medium	Java	[BFS, DFS, Matrix DFS, Union Find]
30	The Maze II.java	Medium	Java	[BFS, DFS, PriorityQueue]
31	The Maze III.java	Hard	Java	[BFS, DFS, PriorityQueue]
32	Binary Tree Preorder Traversal.java	Easy	Java	[BFS, DFS, Stack, Tree]
33	Topological Sorting.java	Medium	Java	[BFS, DFS, Topological Sort]
34	Invert Binary Tree.java	Easy	Java	[BFS, DFS, Tree]
35	Minimum Depth of Binary Tree.java	Easy	Java	[BFS, DFS, Tree]
36	Symmetric Tree.java	Easy	Java	[BFS, DFS, Tree]
37	Binary Tree Level Order Traversal.java	Medium	Java	[BFS, DFS, Tree]
38	Binary Tree Right Side View.java	Medium	Java	[BFS, DFS, Tree]
39	Convert Sorted List to Binary Search Tree.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List]
40	Convert Binary Search Tree to Sorted Doubly Linked List.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List, Tree]
41	Validate Binary Search Tree.java	Medium	Java	[BST, DFS, Divide and Conquer, Tree]
42	Kth Smallest Element in a BST.java	Medium	Java	[BST, DFS, Stack, Tree]
43	Lowest Common Ancestor of a Binary Search Tree.java	Medium	Java	[BST, DFS, Tree]
44	Recover Binary Search Tree.java	Hard	Java	[BST, DFS, Tree]
45	Binary Tree Paths.java	Easy	Java	[Backtracking, Binary Tree, DFS]
46	Combinations.java	Medium	Java	[Backtracking, Combination, DFS]
47	Palindrome Partitioning.java	Medium	Java	[Backtracking, DFS]
48	Robot Room Cleaner.java	Hard	Java	[Backtracking, DFS]
49	Flip Game II.java	Medium	Java	[Backtracking, DFS, DP]
50	Word Break II.java	Hard	Java	[Backtracking, DFS, DP, Hash Table, Memoization]
51	Expression Add Operators.java	Hard	Java	[Backtracking, DFS, Divide and Conquer, String]
52	Permutations.java	Medium	Java	[Backtracking, DFS, Permutation]
53	Generate Parentheses.java	Medium	Java	[Backtracking, DFS, Sequence DFS, String]
54	Restore IP Addresses.java	Medium	Java	[Backtracking, DFS, String]
55	Path Sum II.java	Easy	Java	[Backtracking, DFS, Tree]
56	Word Search II.java	Hard	Java	[Backtracking, DFS, Trie]
57	Find Peak Element II.java	Hard	Java	[Binary Search, DFS, Divide and Conquer]
58	Flatten Binary Tree to Linked List.java	Medium	Java	[Binary Tree, DFS]
59	Segment Tree Query.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
60	Segment Tree Modify.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
61	Segment Tree Query II.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
62	Expression Evaluation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Minimum Binary Tree, Stack]
63	Convert Expression to Polish Notation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Stack]
64	Convert Expression to Reverse Polish Notation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Stack]
65	Longest Increasing Path in a Matrix.java	Hard	Java	[Coordinate DP, DFS, DP, Memoization, Topological Sort]
66	Flood Fill.java	Easy	Java	[DFS]
67	Target Sum.java	Medium	Java	[DFS, DP]
68	Longest Palindromic Subsequence.java	Medium	Java	[DFS, DP, Interval DP, Memoization]
69	House Robber III.java	Medium	Java	[DFS, DP, Status DP, Tree]
70	Binary Tree Maximum Path Sum.java	Hard	Java	[DFS, DP, Tree, Tree DP]
71	Fast Power.java	Medium	Java	[DFS, Divide and Conquer]
72	Binary Tree Longest Consecutive Sequence II.java	Medium	Java	[DFS, Divide and Conquer, Double Recursive, Tree]
73	Decode String.java	Medium	Java	[DFS, Divide and Conquer, Stack]
74	Convert Sorted Array to Binary Search Tree.java	Easy	Java	[DFS, Divide and Conquer, Tree]
75	Populating Next Right Pointers in Each Node.java	Medium	Java	[DFS, Divide and Conquer, Tree]
76	Binary Tree Longest Consecutive Sequence.java	Medium	Java	[DFS, Divide and Conquer, Tree]
77	Smallest Subtree with all the Deepest Nodes.java	Medium	Java	[DFS, Divide and Conquer, Tree]
78	Subtree of Another Tree.java	Easy	Java	[DFS, Divide and Conquer, Tree]
79	Path Sum III.java	Easy	Java	[DFS, Double Recursive, Tree]
80	Strobogrammatic Number II.java	Medium	Java	[DFS, Enumeration, Math, Sequence DFS]
81	Redundant Connection II.java	Hard	Java	[DFS, Graph, Tree, Union Find]
82	Cracking the Safe.java	Hard	Java	[DFS, Greedy, Math]
83	Accounts Merge.java	Medium	Java	[DFS, Hash Table, Hash Table, Union Find]
84	Path Sum IV.java	Medium	Java	[DFS, Hash Table, Tree]
85	Same Tree.java	Easy	Java	[DFS, Tree]
86	Balanced Binary Tree.java	Medium	Java	[DFS, Tree]
87	Maximum Depth of Binary Tree.java	Easy	Java	[DFS, Tree]
88	Tweaked Identical Binary Tree.java	Easy	Java	[DFS, Tree]
89	Merge Two Binary Trees.java	Easy	Java	[DFS, Tree]
90	Subtree.java	Easy	Java	[DFS, Tree]
91	Lowest Common Ancestor of a Binary Tree.java	Medium	Java	[DFS, Tree]
92	Path Sum.java	Easy	Java	[DFS, Tree]
93	Binary Tree Maximum Path Sum II.java	Medium	Java	[DFS, Tree]
94	Populating Next Right Pointers in Each Node II.java	Medium	Java	[DFS, Tree]

DP (85)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Max Sum of Rectangle No Larger Than K.java	Hard	Java	[Array, BST, Binary Search, DP, Queue, TreeSet]
1	Combination Sum IV.java	Medium	Java	[Array, Backpack DP, DP]
2	Triangles.java	Medium	Java	[Array, Coordinate DP, DFS, DP, Memoization]
3	Unique Paths II.java	Medium	Java	[Array, Coordinate DP, DP]
4	Unique Path.java	Medium	Java	[Array, Coordinate DP, DP]
5	Longest Continuous Increasing Subsequence.java	Easy	Java	[Array, Coordinate DP, DP]
6	Minimum Path Sum.java	Medium	Java	[Array, Coordinate DP, DP]
7	Longest Increasing Continuous subsequence.java	Easy	Java	[Array, Coordinate DP, DP]
8	Jump Game II.java	Hard	Java	[Array, Coordinate DP, DP, Greedy]
9	Longest Increasing Continuous subsequence II.java	Medium	Java	[Array, Coordinate DP, DP, Memoization]
10	Maximum Subarray.java	Easy	Java	[Array, DFS, DP, Divide and Conquer, PreSum, Sequence DP, Subarray]
11	Coins in a Line III.java	Hard	Java	[Array, DP, Game Theory, Interval DP, Memoization]
12	Coins in a Line II.java	Medium	Java	[Array, DP, Game Theory, Memoization, MiniMax]
13	Jump Game.java	Medium	Java	[Array, DP, Greedy]
14	Maximum Subarray II.java	Medium	Java	[Array, DP, Greedy, PreSum, Sequence DP, Subarray]
15	Best Time to Buy and Sell Stock II.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Status DP]
16	Best Time to Buy and Sell Stock with Transaction Fee.java	Medium	Java	[Array, DP, Greedy, Sequence DP, Status DP]
17	Minimum Subarray.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Subarray]
18	Maximal Rectangle.java	Hard	Java	[Array, DP, Hash Table, Stack]
19	Best Time to Buy and Sell Stock III.java	Hard	Java	[Array, DP, Sequence DP]
20	Best Time to Buy and Sell Stock.java	Easy	Java	[Array, DP, Sequence DP]
21	Maximum Product Subarray.java	Medium	Java	[Array, DP, Subarray]
22	Remove Invalid Parentheses.java	Review	Java	[BFS, DFS, DP]
23	Perfect Squares.java	Medium	Java	[BFS, DP, Math, Partition DP]
24	Unique Binary Search Tree II.java	Medium	Java	[BST, DP, Divide and Conquer, Tree]
25	Unique Binary Search Tree.java	Medium	Java	[BST, DP, Tree]
26	Backpack VI.java	Medium	Java	[Backpack DP, DP]
27	Coin Change 2.java	Medium	Java	[Backpack DP, DP]
28	Backpack.java	Medium	Java	[Backpack DP, DP]
29	Backpack II.java	Medium	Java	[Backpack DP, DP]
30	Backpack V.java	Medium	Java	[Backpack DP, DP]
31	Backpack III.java	Hard	Java	[Backpack DP, DP]
32	Coin Change.java	Medium	Java	[Backpack DP, DP, Memoization]
33	Flip Game II.java	Medium	Java	[Backtracking, DFS, DP]
34	Word Break II.java	Hard	Java	[Backtracking, DFS, DP, Hash Table, Memoization]
35	Wildcard Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Greedy, Sequence DP, String]
36	Regular Expression Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Sequence DP, String]
37	Russian Doll Envelopes.java	Hard	Java	[Binary Search, Coordinate DP, DP]
38	Longest Increasing Subsequence.java	Medium	Java	[Binary Search, Coordinate DP, DP, Memoization]
39	Copy Books.java	Hard	Java	[Binary Search, DP, Partition DP]
40	Counting Bits.java	Medium	Java	[Bit Manipulation, Bitwise DP, DP]
41	Nim Game.java	Easy	Java	[Brainteaser, DP, Game Theory]
42	Longest Increasing Path in a Matrix.java	Hard	Java	[Coordinate DP, DFS, DP, Memoization, Topological Sort]
43	Bomb Enemy.java	Medium	Java	[Coordinate DP, DP]
44	Maximal Square.java	Medium	Java	[Coordinate DP, DP]
45	Number of Longest Increasing Subsequence.java	Medium	Java	[Coordinate DP, DP]
46	Continuous Subarray Sum.java	Medium	Java	[Coordinate DP, DP, Math, Subarray]
47	Minimum Swaps To Make Sequences Increasing.java	Medium	Java	[Coordinate DP, DP, Status DP]
48	Target Sum.java	Medium	Java	[DFS, DP]
49	Longest Palindromic Subsequence.java	Medium	Java	[DFS, DP, Interval DP, Memoization]
50	House Robber III.java	Medium	Java	[DFS, DP, Status DP, Tree]
51	Binary Tree Maximum Path Sum.java	Hard	Java	[DFS, DP, Tree, Tree DP]
52	Stone Game.java	Medium	Java	[DP]
53	k Sum.java	Hard	Java	[DP]
54	Best Time to Buy and Sell Stock with Cooldown.java	Medium	Java	[DP]
55	Ones and Zeroes.java	Hard	Java	[DP]
56	Maximum Vacation Days.java	Hard	Java	[DP]
57	Burst Balloons.java	Hard	Java	[DP, Divide and Conquer, Interval DP, Memoization]
58	Longest Common Subsequence.java	Medium	Java	[DP, Double Sequence DP, Sequence DP]
59	Edit Distance.java	Hard	Java	[DP, Double Sequence DP, Sequence DP, String]
60	Longest Common Substring.java	Medium	Java	[DP, Double Sequence DP, Sequence DP, String]
61	K Edit Distance.java	Hard	Java	[DP, Double Sequence DP, Sequence DP, Trie]
62	Ugly Number II.java	Medium	Java	[DP, Enumeration, Heap, Math, PriorityQueue]
63	Decode Ways II.java	Hard	Java	[DP, Enumeration, Partition DP]
64	Coins in a Line.java	Medium	Java	[DP, Game Theory, Greedy]
65	Frog Jump.java	Hard	Java	[DP, Hash Table]
66	Word Break.java	Medium	Java	[DP, Hash Table, Sequence DP]
67	Scramble String.java	Hard	Java	[DP, Interval DP, String]
68	Number Of Corner Rectangles.java	Medium	Java	[DP, Math]
69	Fibonacci.java	Easy	Java	[DP, Math, Memoization]
70	Climbing Stairs.java	Easy	Java	[DP, Memoization, Sequence DP]
71	Predict the Winner.java	Medium	Java	[DP, MiniMax]
72	Palindrome Partitioning II.java	Hard	Java	[DP, Partition DP]
73	Decode Ways.java	Medium	Java	[DP, Partition DP, String]
74	Range Sum Query - Immutable.java	Easy	Java	[DP, PreSum]
75	House Robber.java	Easy	Java	[DP, Sequence DP]
76	Best Time to Buy and Sell Stock IV.java	Hard	Java	[DP, Sequence DP]
77	Paint Fence.java	Easy	Java	[DP, Sequence DP]
78	Paint House.java	Easy	Java	[DP, Sequence DP, Status DP]
79	House Robber II.java	Medium	Java	[DP, Sequence DP, Status DP]
80	Paint House II.java	Hard	Java	[DP, Sequence DP, Status DP]
81	Interleaving String.java	Hard	Java	[DP, String]
82	Distinct Subsequences.java	Hard	Java	[DP, String]
83	Longest Palindromic Substring.java	Medium	Java	[DP, String]
84	Palindromic Substrings.java	Medium	Java	[DP, String]

Hash Table (69)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Word Ladder II.java	Hard	Java	[Array, BFS, Backtracking, DFS, Hash Table, String]
1	Construct Binary Tree from Preorder and Inorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Hash Table, Tree]
2	Maximal Rectangle.java	Hard	Java	[Array, DP, Hash Table, Stack]
3	Insert Delete GetRandom O(1).java	Medium	Java	[Array, Design, Hash Table]
4	Max Points on a Line.java	Hard	Java	[Array, Geometry, Hash Table, Math]
5	Contains Duplicate.java	Easy	Java	[Array, Hash Table]
6	Contains Duplicate II.java	Easy	Java	[Array, Hash Table]
7	Two Sum.java	Easy	Java	[Array, Hash Table]
8	Anagrams.java	Medium	Java	[Array, Hash Table]
9	Submatrix Sum.java	Medium	Java	[Array, Hash Table, PreSum]
10	Subarray Sum.java	Easy	Java	[Array, Hash Table, PreSum, Subarray]
11	Subarray Sum Equals K.java	Medium	Java	[Array, Hash Table, PreSum, Subarray]
12	Longest Consecutive Sequence.java	Hard	Java	[Array, Hash Table, Union Find]
13	Binary Tree Vertical Order Traversal.java	Medium	Java	[BFS, DFS, Hash Table, Tree]
14	Word Break II.java	Hard	Java	[Backtracking, DFS, DP, Hash Table, Memoization]
15	Intersection of Two Arrays II.java	Easy	Java	[Binary Search, Hash Table, Sort, Two Pointers]
16	Intersection of Two Arrays.java	Easy	Java	[Binary Search, Hash Table, Sort, Two Pointers]
17	H-Index.java	Medium	Java	[Bucket Sort, Hash Table, Sort]
18	Accounts Merge.java	Medium	Java	[DFS, Hash Table, Hash Table, Union Find]
19	Accounts Merge.java	Medium	Java	[DFS, Hash Table, Hash Table, Union Find]
20	Path Sum IV.java	Medium	Java	[DFS, Hash Table, Tree]
21	Frog Jump.java	Hard	Java	[DP, Hash Table]
22	Word Break.java	Medium	Java	[DP, Hash Table, Sequence DP]
23	Perfect Rectangle.java	Hard	Java	[Design, Geometry, Hash Table]
24	LFU Cache.java	Hard	Java	[Design, Hash Table]
25	Unique Word Abbreviation.java	Medium	Java	[Design, Hash Table]
26	ColorGrid.java	Medium	Java	[Design, Hash Table]
27	LRU Cache.java	Hard	Java	[Design, Hash Table, Linked List]
28	Design Search Autocomplete System.java	Hard	Java	[Design, Hash Table, MinHeap, PriorityQueue, Trie]
29	Valid Sudoku.java	Easy	Java	[Enumeration, Hash Table]
30	Strobogrammatic Number.java	Easy	Java	[Enumeration, Hash Table, Math]
31	Rearrange String k Distance Apart.java	Hard	Java	[Greedy, Hash Table, Heap]
32	Remove Duplicate Letters.java	Hard	Java	[Greedy, Hash Table, Stack]
33	Jewels and Stones.java	Easy	Java	[Hash Table]
34	Find Anagram Mappings.java	Easy	Java	[Hash Table]
35	Island Perimeter.java	Easy	Java	[Hash Table]
36	Palindrome Permutation.java	Easy	Java	[Hash Table]
37	Hash Function.java	Easy	Java	[Hash Table]
38	HashWithCustomizedClass(LinkedList).java	Medium	Java	[Hash Table]
39	Rehashing.java	Medium	Java	[Hash Table]
40	Sparse Matrix Multiplication.java	Medium	Java	[Hash Table]
41	Brick Wall.java	Medium	Java	[Hash Table]
42	Contiguous Array.java	Medium	Java	[Hash Table]
43	4Sum.java	Medium	Java	[Hash Table]
44	Isomorphic Strings.java	Easy	Java	[Hash Table]
45	Top K Frequent Elements.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue]
46	Top K Frequent Words.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue, Trie]
47	Majority Number III.java	Medium	Java	[Hash Table, Linked List]
48	Copy List with Random Pointer.java	Medium	Java	[Hash Table, Linked List]
49	Fraction to Recurring Decimal.java	Medium	Java	[Hash Table, Math]
50	Encode and Decode TinyURL.java	Medium	Java	[Hash Table, Math]
51	Count Primes.java	Easy	Java	[Hash Table, Math]
52	Line Reflection.java	Medium	Java	[Hash Table, Math]
53	Maximum Size Subarray Sum Equals k.java	Medium	Java	[Hash Table, PreSum, Subarray]
54	Find All Anagrams in a String.java	Easy	Java	[Hash Table, Sliding Window]
55	Longest Substring with At Most K Distinct Characters.java	Hard	Java	[Hash Table, Sliding Window, String]
56	Longest Substring with At Most Two Distinct Characters.java	Hard	Java	[Hash Table, Sliding Window, String, Two Pointers]
57	Valid Anagram.java	Easy	Java	[Hash Table, Sort]
58	Next Greater Element I.java	Easy	Java	[Hash Table, Stack]
59	Binary Tree Inorder Traversal.java	Easy	Java	[Hash Table, Stack, Tree]
60	Group Anagrams.java	Medium	Java	[Hash Table, String]
61	Longest Words.java	Easy	Java	[Hash Table, String]
62	First Unique Character in a String.java	Easy	Java	[Hash Table, String]
63	Group Shifted Strings.java	Medium	Java	[Hash Table, String]
64	Palindrome Pairs.java	Hard	Java	[Hash Table, String, Trie]
65	Longest Substring Without Repeating Characters.java	Medium	Java	[Hash Table, String, Two Pointers]
66	Minimum Window Substring.java	Hard	Java	[Hash Table, String, Two Pointers]
67	Lowest Common Ancestor II.java	Easy	Java	[Hash Table, Tree]
68	Longest Word in Dictionary.java	Easy	Java	[Hash Table, Trie]

String (60)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Word Ladder II.java	Hard	Java	[Array, BFS, Backtracking, DFS, Hash Table, String]
1	Unique Characters.java	Easy	Java	[Array, String]
2	Expression Add Operators.java	Hard	Java	[Backtracking, DFS, Divide and Conquer, String]
3	Generate Parentheses.java	Medium	Java	[Backtracking, DFS, Sequence DFS, String]
4	Restore IP Addresses.java	Medium	Java	[Backtracking, DFS, String]
5	Wildcard Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Greedy, Sequence DP, String]
6	Regular Expression Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Sequence DP, String]
7	Letter Combinations of a Phone Number.java	Medium	Java	[Backtracking, String]
8	Next Closest Time.java	Medium	Java	[Basic Implementation, Enumeration, String]
9	Count and Say.java	Easy	Java	[Basic Implementation, String]
10	Binary Representation.java	Hard	Java	[Bit Manipulation, String]
11	Longest Valid Parentheses.java	Hard	Java	[Coordinate DP, Stack, String]
12	Edit Distance.java	Hard	Java	[DP, Double Sequence DP, Sequence DP, String]
13	Longest Common Substring.java	Medium	Java	[DP, Double Sequence DP, Sequence DP, String]
14	Scramble String.java	Hard	Java	[DP, Interval DP, String]
15	Decode Ways.java	Medium	Java	[DP, Partition DP, String]
16	Interleaving String.java	Hard	Java	[DP, String]
17	Distinct Subsequences.java	Hard	Java	[DP, String]
18	Longest Palindromic Substring.java	Medium	Java	[DP, String]
19	Palindromic Substrings.java	Medium	Java	[DP, String]
20	Valid Number.java	Hard	Java	[Enumeration, Math, String]
21	Integer to English Words.java	Hard	Java	[Enumeration, Math, String]
22	Read N Characters Given Read4.java	Easy	Java	[Enumeration, String]
23	Text Justification.java	Hard	Java	[Enumeration, String]
24	Read N Characters Given Read4 II - Call multiple times.java	Hard	Java	[Enumeration, String]
25	Longest Substring with At Most K Distinct Characters.java	Hard	Java	[Hash Table, Sliding Window, String]
26	Longest Substring with At Most Two Distinct Characters.java	Hard	Java	[Hash Table, Sliding Window, String, Two Pointers]
27	Group Anagrams.java	Medium	Java	[Hash Table, String]
28	Longest Words.java	Easy	Java	[Hash Table, String]
29	First Unique Character in a String.java	Easy	Java	[Hash Table, String]
30	Group Shifted Strings.java	Medium	Java	[Hash Table, String]
31	Palindrome Pairs.java	Hard	Java	[Hash Table, String, Trie]
32	Longest Substring Without Repeating Characters.java	Medium	Java	[Hash Table, String, Two Pointers]
33	Minimum Window Substring.java	Hard	Java	[Hash Table, String, Two Pointers]
34	Shortest Palindrome.java	Hard	Java	[KMP, String]
35	Multiply Strings.java	Medium	Java	[Math, String]
36	String to Integer (atoi).java	Medium	Java	[Math, String]
37	Roman to Integer.java	Easy	Java	[Math, String]
38	Add Binary.java	Easy	Java	[Math, String, Two Pointers]
39	Sort Letters by Case.java	Medium	Java	[Partition, Sort, String, Two Pointers]
40	Simplify Path.java	Medium	Java	[Stack, String]
41	Valid Parentheses.java	Easy	Java	[Stack, String]
42	Space Replacement.java	Medium	Java	[String]
43	Judge Route Circle.java	Easy	Java	[String]
44	Change to Anagram.java	Easy	Java	[String]
45	Compare Version Numbers.java	Medium	Java	[String]
46	Compare Strings.java	Easy	Java	[String]
47	Flip Game.java	Easy	Java	[String]
48	Length of Last Word.java	Easy	Java	[String]
49	Rotate String.java	Easy	Java	[String]
50	Encode and Decode Strings.java	Medium	Java	[String]
51	Longest Common Prefix.java	Easy	Java	[String]
52	Reverse Words in a String.java	Medium	Java	[String]
53	Reverse Words in a String II.java	Medium	Java	[String]
54	Reverse Words in a String III.java	Easy	Java	[String]
55	Valid Palindrome II.java	Easy	Java	[String]
56	One Edit Distance.java	Medium	Java	[String]
57	Reverse Vowels of a String.java	Easy	Java	[String, Two Pointers]
58	Implement strStr().java	Easy	Java	[String, Two Pointers]
59	Valid Palindrome.java	Easy	Java	[String, Two Pointers]

Tree (55)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Construct Binary Tree from Preorder and Inorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Hash Table, Tree]
1	Construct Binary Tree from Inorder and Postorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Tree]
2	Serialize and Deserialize Binary Tree.java	Hard	Java	[BFS, DFS, Deque, Design, Divide and Conquer, Tree]
3	Redundant Connection.java	Medium	Java	[BFS, DFS, Graph, Tree, Union Find]
4	Binary Tree Vertical Order Traversal.java	Medium	Java	[BFS, DFS, Hash Table, Tree]
5	Binary Tree Preorder Traversal.java	Easy	Java	[BFS, DFS, Stack, Tree]
6	Invert Binary Tree.java	Easy	Java	[BFS, DFS, Tree]
7	Minimum Depth of Binary Tree.java	Easy	Java	[BFS, DFS, Tree]
8	Symmetric Tree.java	Easy	Java	[BFS, DFS, Tree]
9	Binary Tree Level Order Traversal.java	Medium	Java	[BFS, DFS, Tree]
10	Binary Tree Right Side View.java	Medium	Java	[BFS, DFS, Tree]
11	Binary Tree Zigzag Level Order Traversal.java	Medium	Java	[BFS, Stack, Tree]
12	Complete Binary Tree.java	Easy	Java	[BFS, Tree]
13	Binary Tree Level Order Traversal II.java	Medium	Java	[BFS, Tree]
14	Closest Binary Search Tree Value.java	Easy	Java	[BST, Binary Search, Tree]
15	Convert Binary Search Tree to Sorted Doubly Linked List.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List, Tree]
16	Validate Binary Search Tree.java	Medium	Java	[BST, DFS, Divide and Conquer, Tree]
17	Kth Smallest Element in a BST.java	Medium	Java	[BST, DFS, Stack, Tree]
18	Lowest Common Ancestor of a Binary Search Tree.java	Medium	Java	[BST, DFS, Tree]
19	Recover Binary Search Tree.java	Hard	Java	[BST, DFS, Tree]
20	Unique Binary Search Tree II.java	Medium	Java	[BST, DP, Divide and Conquer, Tree]
21	Unique Binary Search Tree.java	Medium	Java	[BST, DP, Tree]
22	Binary Search Tree Iterator.java	Medium	Java	[BST, Design, Stack, Tree]
23	Trim a Binary Search Tree.java	Easy	Java	[BST, Tree]
24	Inorder Successor in BST.java	Medium	Java	[BST, Tree]
25	Path Sum II.java	Easy	Java	[Backtracking, DFS, Tree]
26	Count Complete Tree Nodes.java	Medium	Java	[Binary Search, Tree]
27	House Robber III.java	Medium	Java	[DFS, DP, Status DP, Tree]
28	Binary Tree Maximum Path Sum.java	Hard	Java	[DFS, DP, Tree, Tree DP]
29	Binary Tree Longest Consecutive Sequence II.java	Medium	Java	[DFS, Divide and Conquer, Double Recursive, Tree]
30	Convert Sorted Array to Binary Search Tree.java	Easy	Java	[DFS, Divide and Conquer, Tree]
31	Populating Next Right Pointers in Each Node.java	Medium	Java	[DFS, Divide and Conquer, Tree]
32	Binary Tree Longest Consecutive Sequence.java	Medium	Java	[DFS, Divide and Conquer, Tree]
33	Smallest Subtree with all the Deepest Nodes.java	Medium	Java	[DFS, Divide and Conquer, Tree]
34	Subtree of Another Tree.java	Easy	Java	[DFS, Divide and Conquer, Tree]
35	Path Sum III.java	Easy	Java	[DFS, Double Recursive, Tree]
36	Redundant Connection II.java	Hard	Java	[DFS, Graph, Tree, Union Find]
37	Path Sum IV.java	Medium	Java	[DFS, Hash Table, Tree]
38	Same Tree.java	Easy	Java	[DFS, Tree]
39	Balanced Binary Tree.java	Medium	Java	[DFS, Tree]
40	Maximum Depth of Binary Tree.java	Easy	Java	[DFS, Tree]
41	Tweaked Identical Binary Tree.java	Easy	Java	[DFS, Tree]
42	Merge Two Binary Trees.java	Easy	Java	[DFS, Tree]
43	Subtree.java	Easy	Java	[DFS, Tree]
44	Lowest Common Ancestor of a Binary Tree.java	Medium	Java	[DFS, Tree]
45	Path Sum.java	Easy	Java	[DFS, Tree]
46	Binary Tree Maximum Path Sum II.java	Medium	Java	[DFS, Tree]
47	Populating Next Right Pointers in Each Node II.java	Medium	Java	[DFS, Tree]
48	Binary Tree Inorder Traversal.java	Easy	Java	[Hash Table, Stack, Tree]
49	Lowest Common Ancestor II.java	Easy	Java	[Hash Table, Tree]
50	Convert Binary Search Tree to Sorted Doubly Linked List (extra space).java	Medium	Java	[Linked List, Stack, Tree]
51	Maximum Binary Tree.java	Medium	Java	[Stack, Tree]
52	Binary Tree Postorder Traversal.java	Medium	Java	[Stack, Tree, Two Stacks]
53	Two Sum IV - Input is a BST.java	Easy	Java	[Tree]
54	Diameter of Binary Tree.java	Easy	Java	[Tree]

Binary Search (40)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Max Sum of Rectangle No Larger Than K.java	Hard	Java	[Array, BST, Binary Search, DP, Queue, TreeSet]
1	Search in Rotated Sorted Array II.java	Medium	Java	[Array, Binary Search]
2	Find Peak Element.java	Medium	Java	[Array, Binary Search]
3	Find Minimum in Rotated Sorted Array.java	Medium	Java	[Array, Binary Search]
4	Find Minimum in Rotated Sorted Array II.java	Hard	Java	[Array, Binary Search]
5	Search a 2D Matrix.java	Medium	Java	[Array, Binary Search]
6	Search for a Range.java	Medium	Java	[Array, Binary Search]
7	Search in Rotated Sorted Array.java	Medium	Java	[Array, Binary Search]
8	Median of Two Sorted Arrays.java	Hard	Java	[Array, Binary Search, DFS, Divide and Conquer]
9	Maximum Average Subarray II.java	Review	Java	[Array, Binary Search, PreSum]
10	Minimum Size Subarray Sum.java	Medium	Java	[Array, Binary Search, Subarray, Two Pointers]
11	Subarray Sum II.java	Hard	Java	[Array, Binary Search, Two Pointers]
12	Two Sum II - Input array is sorted.java	Medium	Java	[Array, Binary Search, Two Pointers]
13	2 Sum II.java	Medium	Java	[Array, Binary Search, Two Pointers]
14	Find the Duplicate Number.java	Medium	Java	[Array, Binary Search, Two Pointers]
15	Count of Smaller Numbers After Self.java	Hard	Java	[BST, Binary Indexed Tree, Binary Search, Divide and Conquer, Segment Tree]
16	Closest Binary Search Tree Value.java	Easy	Java	[BST, Binary Search, Tree]
17	Guess Number Higher or Lower.java	Easy	Java	[Binary Search]
18	First Bad Version.java	Easy	Java	[Binary Search]
19	Wood Cut.java	Medium	Java	[Binary Search]
20	Classical Binary Search.java	Easy	Java	[Binary Search]
21	Closest Number in Sorted Array.java	Easy	Java	[Binary Search]
22	Last Position of Target.java	Easy	Java	[Binary Search]
23	H-Index II.java	Medium	Java	[Binary Search]
24	Russian Doll Envelopes.java	Hard	Java	[Binary Search, Coordinate DP, DP]
25	Longest Increasing Subsequence.java	Medium	Java	[Binary Search, Coordinate DP, DP, Memoization]
26	Find Peak Element II.java	Hard	Java	[Binary Search, DFS, Divide and Conquer]
27	Copy Books.java	Hard	Java	[Binary Search, DP, Partition DP]
28	Search a 2D Matrix II.java	Medium	Java	[Binary Search, Divide and Conquer]
29	Interval Minimum Number.java	Medium	Java	[Binary Search, Divide and Conquer, Lint, Segment Tree]
30	Intersection of Two Arrays II.java	Easy	Java	[Binary Search, Hash Table, Sort, Two Pointers]
31	Intersection of Two Arrays.java	Easy	Java	[Binary Search, Hash Table, Sort, Two Pointers]
32	Kth Smallest Element in a Sorted Matrix.java	Medium	Java	[Binary Search, Heap]
33	Interval Sum.java	Medium	Java	[Binary Search, Lint, Segment Tree]
34	Interval Sum II.java	Hard	Java	[Binary Search, Lint, Segment Tree]
35	Count of Smaller Number.java	Medium	Java	[Binary Search, Lint, Segment Tree]
36	Valid Perfect Square.java	Review	Java	[Binary Search, Math]
37	Pow(x, n).java	Medium	Java	[Binary Search, Math]
38	Sqrt(x).java	Easy	Java	[Binary Search, Math]
39	Count Complete Tree Nodes.java	Medium	Java	[Binary Search, Tree]

BFS (39)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Subsets.java	Medium	Java	[Array, BFS, Backtracking, Bit Manipulation, DFS]
1	Subsets II.java	Medium	Java	[Array, BFS, Backtracking, DFS]
2	Word Ladder II.java	Hard	Java	[Array, BFS, Backtracking, DFS, Hash Table, String]
3	Word Ladder.java	Medium	Java	[BFS]
4	Shortest Distance from All Buildings.java	Hard	Java	[BFS]
5	Bus Routes.java	Hard	Java	[BFS]
6	Course Schedule.java	Medium	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
7	Alien Dictionary.java	Hard	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
8	Nested List Weight Sum.java	Easy	Java	[BFS, DFS]
9	Find the Connected Component in the Undirected Graph.java	Medium	Java	[BFS, DFS]
10	Walls and Gates.java	Medium	Java	[BFS, DFS]
11	The Maze.java	Medium	Java	[BFS, DFS]
12	Remove Invalid Parentheses.java	Review	Java	[BFS, DFS, DP]
13	Serialize and Deserialize Binary Tree.java	Hard	Java	[BFS, DFS, Deque, Design, Divide and Conquer, Tree]
14	Clone Graph.java	Medium	Java	[BFS, DFS, Graph]
15	Course Schedule II.java	Medium	Java	[BFS, DFS, Graph, Topological Sort]
16	Redundant Connection.java	Medium	Java	[BFS, DFS, Graph, Tree, Union Find]
17	Evaluate Division.java	Medium	Java	[BFS, DFS, Graph, Union Find]
18	Number of Connected Components in an Undirected Graph.java	Medium	Java	[BFS, DFS, Graph, Union Find]
19	Graph Valid Tree.java	Medium	Java	[BFS, DFS, Graph, Union Find]
20	Binary Tree Vertical Order Traversal.java	Medium	Java	[BFS, DFS, Hash Table, Tree]
21	Number of Islands.java	Medium	Java	[BFS, DFS, Matrix DFS, Union Find]
22	Surrounded Regions.java	Medium	Java	[BFS, DFS, Matrix DFS, Union Find]
23	The Maze II.java	Medium	Java	[BFS, DFS, PriorityQueue]
24	The Maze III.java	Hard	Java	[BFS, DFS, PriorityQueue]
25	Binary Tree Preorder Traversal.java	Easy	Java	[BFS, DFS, Stack, Tree]
26	Topological Sorting.java	Medium	Java	[BFS, DFS, Topological Sort]
27	Invert Binary Tree.java	Easy	Java	[BFS, DFS, Tree]
28	Minimum Depth of Binary Tree.java	Easy	Java	[BFS, DFS, Tree]
29	Symmetric Tree.java	Easy	Java	[BFS, DFS, Tree]
30	Binary Tree Level Order Traversal.java	Medium	Java	[BFS, DFS, Tree]
31	Binary Tree Right Side View.java	Medium	Java	[BFS, DFS, Tree]
32	Perfect Squares.java	Medium	Java	[BFS, DP, Math, Partition DP]
33	Minimum Height Trees.java	Medium	Java	[BFS, Graph]
34	Sliding Puzzle.java	Hard	Java	[BFS, Graph]
35	Trapping Rain Water II.java	Hard	Java	[BFS, Heap, MinHeap, PriorityQueue]
36	Binary Tree Zigzag Level Order Traversal.java	Medium	Java	[BFS, Stack, Tree]
37	Complete Binary Tree.java	Easy	Java	[BFS, Tree]
38	Binary Tree Level Order Traversal II.java	Medium	Java	[BFS, Tree]

Math (38)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Missing Number.java	Easy	Java	[Array, Bit Manipulation, Math]
1	Max Points on a Line.java	Hard	Java	[Array, Geometry, Hash Table, Math]
2	Plus One.java	Easy	Java	[Array, Math]
3	Friends Of Appropriate Ages.java	Medium	Java	[Array, Math]
4	Perfect Squares.java	Medium	Java	[BFS, DP, Math, Partition DP]
5	Permutation Sequence.java	Medium	Java	[Backtracking, Math]
6	Valid Perfect Square.java	Review	Java	[Binary Search, Math]
7	Pow(x, n).java	Medium	Java	[Binary Search, Math]
8	Sqrt(x).java	Easy	Java	[Binary Search, Math]
9	Basic Calculator.java	Hard	Java	[Binary Tree, Expression Tree, Math, Minimum Binary Tree, Stack]
10	Power of Two.java	Easy	Java	[Bit Manipulation, Math]
11	Continuous Subarray Sum.java	Medium	Java	[Coordinate DP, DP, Math, Subarray]
12	Strobogrammatic Number II.java	Medium	Java	[DFS, Enumeration, Math, Sequence DFS]
13	Cracking the Safe.java	Hard	Java	[DFS, Greedy, Math]
14	Ugly Number II.java	Medium	Java	[DP, Enumeration, Heap, Math, PriorityQueue]
15	Number Of Corner Rectangles.java	Medium	Java	[DP, Math]
16	Fibonacci.java	Easy	Java	[DP, Math, Memoization]
17	Strobogrammatic Number.java	Easy	Java	[Enumeration, Hash Table, Math]
18	Valid Number.java	Hard	Java	[Enumeration, Math, String]
19	Integer to English Words.java	Hard	Java	[Enumeration, Math, String]
20	Fraction to Recurring Decimal.java	Medium	Java	[Hash Table, Math]
21	Encode and Decode TinyURL.java	Medium	Java	[Hash Table, Math]
22	Count Primes.java	Easy	Java	[Hash Table, Math]
23	Line Reflection.java	Medium	Java	[Hash Table, Math]
24	Add Two Numbers.java	Medium	Java	[Linked List, Math]
25	Linked List Cycle II.java	Medium	Java	[Linked List, Math, Two Pointers]
26	Trailing Zeros.java	Easy	Java	[Math]
27	Power of Three.java	Easy	Java	[Math]
28	Add Digits.java	Easy	Java	[Math]
29	Reverse Integer.java	Easy	Java	[Math]
30	Excel Sheet Column Number.java	Easy	Java	[Math]
31	Excel Sheet Column Title.java	Easy	Java	[Math]
32	Ugly Number.java	Medium	Java	[Math]
33	Number of Digit One.java	Hard	Java	[Math]
34	Multiply Strings.java	Medium	Java	[Math, String]
35	String to Integer (atoi).java	Medium	Java	[Math, String]
36	Roman to Integer.java	Easy	Java	[Math, String]
37	Add Binary.java	Easy	Java	[Math, String, Two Pointers]

Two Pointers (38)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Minimum Size Subarray Sum.java	Medium	Java	[Array, Binary Search, Subarray, Two Pointers]
1	Subarray Sum II.java	Hard	Java	[Array, Binary Search, Two Pointers]
2	Two Sum II - Input array is sorted.java	Medium	Java	[Array, Binary Search, Two Pointers]
3	2 Sum II.java	Medium	Java	[Array, Binary Search, Two Pointers]
4	Find the Duplicate Number.java	Medium	Java	[Array, Binary Search, Two Pointers]
5	Sort Colors.java	Medium	Java	[Array, Partition, Quick Sort, Sort, Two Pointers]
6	Partition Array.java	Medium	Java	[Array, Quick Sort, Sort, Two Pointers]
7	The Smallest Difference.java	Medium	Java	[Array, Sort, Two Pointers]
8	Trapping Rain Water.java	Hard	Java	[Array, Stack, Two Pointers]
9	Partition Array by Odd and Even.java	Easy	Java	[Array, Two Pointers]
10	3 Sum Closest.java	Medium	Java	[Array, Two Pointers]
11	3Sum.java	Medium	Java	[Array, Two Pointers]
12	3Sum Smaller.java	Medium	Java	[Array, Two Pointers]
13	Remove Duplicates from Sorted Array.java	Easy	Java	[Array, Two Pointers]
14	Remove Duplicates from Sorted Array II.java	Medium	Java	[Array, Two Pointers]
15	Container With Most Water.java	Medium	Java	[Array, Two Pointers]
16	Merge Sorted Array.java	Easy	Java	[Array, Two Pointers]
17	Move Zeroes.java	Easy	Java	[Array, Two Pointers]
18	Intersection of Two Arrays II.java	Easy	Java	[Binary Search, Hash Table, Sort, Two Pointers]
19	Intersection of Two Arrays.java	Easy	Java	[Binary Search, Hash Table, Sort, Two Pointers]
20	Longest Substring with At Most Two Distinct Characters.java	Hard	Java	[Hash Table, Sliding Window, String, Two Pointers]
21	Longest Substring Without Repeating Characters.java	Medium	Java	[Hash Table, String, Two Pointers]
22	Minimum Window Substring.java	Hard	Java	[Hash Table, String, Two Pointers]
23	Linked List Cycle II.java	Medium	Java	[Linked List, Math, Two Pointers]
24	Linked List Cycle.java	Easy	Java	[Linked List, Two Pointers]
25	Remove Nth Node From End of List.java	Medium	Java	[Linked List, Two Pointers]
26	Palindrome Linked List.java	Easy	Java	[Linked List, Two Pointers]
27	Rotate List.java	Medium	Java	[Linked List, Two Pointers]
28	Partition List.java	Medium	Java	[Linked List, Two Pointers]
29	Add Binary.java	Easy	Java	[Math, String, Two Pointers]
30	Sort Colors II.java	Medium	Java	[Partition, Quick Sort, Sort, Two Pointers]
31	Sort Letters by Case.java	Medium	Java	[Partition, Sort, String, Two Pointers]
32	Backspace String Compare.java	Easy	Java	[Stack, Two Pointers]
33	Reverse Vowels of a String.java	Easy	Java	[String, Two Pointers]
34	Implement strStr().java	Easy	Java	[String, Two Pointers]
35	Valid Palindrome.java	Easy	Java	[String, Two Pointers]
36	Permutation in String.java	Medium	Java	[Two Pointers]
37	Interleaving Positive and Negative Numbers.java	Medium	Java	[Two Pointers]

Divide and Conquer (35)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Median of Two Sorted Arrays.java	Hard	Java	[Array, Binary Search, DFS, Divide and Conquer]
1	Majority Element.java	Easy	Java	[Array, Bit Manipulation, Divide and Conquer]
2	Maximum Subarray.java	Easy	Java	[Array, DFS, DP, Divide and Conquer, PreSum, Sequence DP, Subarray]
3	Construct Binary Tree from Preorder and Inorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Hash Table, Tree]
4	Construct Binary Tree from Inorder and Postorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Tree]
5	Serialize and Deserialize Binary Tree.java	Hard	Java	[BFS, DFS, Deque, Design, Divide and Conquer, Tree]
6	Count of Smaller Numbers After Self.java	Hard	Java	[BST, Binary Indexed Tree, Binary Search, Divide and Conquer, Segment Tree]
7	Convert Sorted List to Binary Search Tree.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List]
8	Convert Binary Search Tree to Sorted Doubly Linked List.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List, Tree]
9	Validate Binary Search Tree.java	Medium	Java	[BST, DFS, Divide and Conquer, Tree]
10	Unique Binary Search Tree II.java	Medium	Java	[BST, DP, Divide and Conquer, Tree]
11	Count of Range Sum.java	Hard	Java	[BST, Divide and Conquer, Merge Sort, PreSum]
12	Expression Add Operators.java	Hard	Java	[Backtracking, DFS, Divide and Conquer, String]
13	Reverse Pairs.java	Medium	Java	[Binary Indexed Tree, Binary Search Tree, Divide and Conquer, Merge Sort, Segment Tree]
14	The Skyline Problem.java	Review	Java	[Binary Indexed Tree, Divide and Conquer, Heap, PriorityQueue, Segment Tree, Sweep Line]
15	Find Peak Element II.java	Hard	Java	[Binary Search, DFS, Divide and Conquer]
16	Search a 2D Matrix II.java	Medium	Java	[Binary Search, Divide and Conquer]
17	Interval Minimum Number.java	Medium	Java	[Binary Search, Divide and Conquer, Lint, Segment Tree]
18	Segment Tree Query.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
19	Segment Tree Modify.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
20	Segment Tree Query II.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
21	Segment Tree Build.java	Medium	Java	[Binary Tree, Divide and Conquer, Lint, Segment Tree]
22	Segment Tree Build II.java	Medium	Java	[Binary Tree, Divide and Conquer, Lint, Segment Tree]
23	Fast Power.java	Medium	Java	[DFS, Divide and Conquer]
24	Binary Tree Longest Consecutive Sequence II.java	Medium	Java	[DFS, Divide and Conquer, Double Recursive, Tree]
25	Decode String.java	Medium	Java	[DFS, Divide and Conquer, Stack]
26	Convert Sorted Array to Binary Search Tree.java	Easy	Java	[DFS, Divide and Conquer, Tree]
27	Populating Next Right Pointers in Each Node.java	Medium	Java	[DFS, Divide and Conquer, Tree]
28	Binary Tree Longest Consecutive Sequence.java	Medium	Java	[DFS, Divide and Conquer, Tree]
29	Smallest Subtree with all the Deepest Nodes.java	Medium	Java	[DFS, Divide and Conquer, Tree]
30	Subtree of Another Tree.java	Easy	Java	[DFS, Divide and Conquer, Tree]
31	Burst Balloons.java	Hard	Java	[DP, Divide and Conquer, Interval DP, Memoization]
32	Merge k Sorted Lists.java	Medium	Java	[Divide and Conquer, Heap, Linked List, PriorityQueue]
33	Kth Largest Element in an Array.java	Medium	Java	[Divide and Conquer, Heap, MinHeap, PriorityQueue, Quick Sort]
34	Sort List.java	Medium	Java	[Divide and Conquer, Linked List, Merge Sort, Sort]

Backtracking (32)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Subsets.java	Medium	Java	[Array, BFS, Backtracking, Bit Manipulation, DFS]
1	Subsets II.java	Medium	Java	[Array, BFS, Backtracking, DFS]
2	Word Ladder II.java	Hard	Java	[Array, BFS, Backtracking, DFS, Hash Table, String]
3	Combination Sum.java	Medium	Java	[Array, Backtracking, Combination, DFS]
4	Combination Sum II.java	Medium	Java	[Array, Backtracking, Combination, DFS]
5	Combination Sum III.java	Medium	Java	[Array, Backtracking, Combination, DFS]
6	Word Search.java	Medium	Java	[Array, Backtracking, DFS]
7	Course Schedule.java	Medium	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
8	Alien Dictionary.java	Hard	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
9	Gray Code.java	Medium	Java	[Backtracking]
10	Permutations II.java	Medium	Java	[Backtracking]
11	N-Queens.java	Hard	Java	[Backtracking]
12	N-Queens II.java	Hard	Java	[Backtracking]
13	Binary Tree Paths.java	Easy	Java	[Backtracking, Binary Tree, DFS]
14	Combinations.java	Medium	Java	[Backtracking, Combination, DFS]
15	Palindrome Partitioning.java	Medium	Java	[Backtracking, DFS]
16	Robot Room Cleaner.java	Hard	Java	[Backtracking, DFS]
17	Flip Game II.java	Medium	Java	[Backtracking, DFS, DP]
18	Word Break II.java	Hard	Java	[Backtracking, DFS, DP, Hash Table, Memoization]
19	Expression Add Operators.java	Hard	Java	[Backtracking, DFS, Divide and Conquer, String]
20	Permutations.java	Medium	Java	[Backtracking, DFS, Permutation]
21	Generate Parentheses.java	Medium	Java	[Backtracking, DFS, Sequence DFS, String]
22	Restore IP Addresses.java	Medium	Java	[Backtracking, DFS, String]
23	Path Sum II.java	Easy	Java	[Backtracking, DFS, Tree]
24	Word Search II.java	Hard	Java	[Backtracking, DFS, Trie]
25	Wildcard Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Greedy, Sequence DP, String]
26	Regular Expression Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Sequence DP, String]
27	Add and Search Word - Data structure design.java	Medium	Java	[Backtracking, Design, Trie]
28	Permutation Sequence.java	Medium	Java	[Backtracking, Math]
29	Palindrome Permutation II.java	Medium	Java	[Backtracking, Permutation]
30	Letter Combinations of a Phone Number.java	Medium	Java	[Backtracking, String]
31	Word Squares.java	Hard	Java	[Backtracking, Trie]

Linked List (31)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Convert Sorted List to Binary Search Tree.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List]
1	Convert Binary Search Tree to Sorted Doubly Linked List.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List, Tree]
2	LRU Cache.java	Hard	Java	[Design, Hash Table, Linked List]
3	Merge k Sorted Lists.java	Medium	Java	[Divide and Conquer, Heap, Linked List, PriorityQueue]
4	Sort List.java	Medium	Java	[Divide and Conquer, Linked List, Merge Sort, Sort]
5	Majority Number III.java	Medium	Java	[Hash Table, Linked List]
6	Copy List with Random Pointer.java	Medium	Java	[Hash Table, Linked List]
7	Remove Duplicates from Unsorted List.java	Medium	Java	[Linked List]
8	Two Lists Sum.java	Medium	Java	[Linked List]
9	Add Two Numbers II.java	Medium	Java	[Linked List]
10	Swap Nodes in Pairs.java	Medium	Java	[Linked List]
11	Delete Node in a Linked List.java	Easy	Java	[Linked List]
12	Middle of Linked List.java	Easy	Java	[Linked List]
13	Remove Linked List Elements.java	Easy	Java	[Linked List]
14	Reverse Linked List.java	Easy	Java	[Linked List]
15	Reverse Linked List II .java	Medium	Java	[Linked List]
16	Intersection of Two Linked Lists.java	Easy	Java	[Linked List]
17	Merge Two Sorted Lists.java	Easy	Java	[Linked List]
18	Remove Duplicates from Sorted List.java	Easy	Java	[Linked List]
19	Remove Duplicates from Sorted List II.java	Medium	Java	[Linked List]
20	Reorder List.java	Medium	Java	[Linked List]
21	Nth to Last Node in List.java	Easy	Java	[Linked List]
22	Add Two Numbers.java	Medium	Java	[Linked List, Math]
23	Linked List Cycle II.java	Medium	Java	[Linked List, Math, Two Pointers]
24	Insertion Sort List.java	Medium	Java	[Linked List, Sort]
25	Convert Binary Search Tree to Sorted Doubly Linked List (extra space).java	Medium	Java	[Linked List, Stack, Tree]
26	Linked List Cycle.java	Easy	Java	[Linked List, Two Pointers]
27	Remove Nth Node From End of List.java	Medium	Java	[Linked List, Two Pointers]
28	Palindrome Linked List.java	Easy	Java	[Linked List, Two Pointers]
29	Rotate List.java	Medium	Java	[Linked List, Two Pointers]
30	Partition List.java	Medium	Java	[Linked List, Two Pointers]

Stack (30)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Maximal Rectangle.java	Hard	Java	[Array, DP, Hash Table, Stack]
1	Largest Rectangle in Histogram.java	Hard	Java	[Array, Monotonous Stack, Stack]
2	Trapping Rain Water.java	Hard	Java	[Array, Stack, Two Pointers]
3	Binary Tree Preorder Traversal.java	Easy	Java	[BFS, DFS, Stack, Tree]
4	Binary Tree Zigzag Level Order Traversal.java	Medium	Java	[BFS, Stack, Tree]
5	Kth Smallest Element in a BST.java	Medium	Java	[BST, DFS, Stack, Tree]
6	Binary Search Tree Iterator.java	Medium	Java	[BST, Design, Stack, Tree]
7	Expression Evaluation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Minimum Binary Tree, Stack]
8	Convert Expression to Polish Notation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Stack]
9	Convert Expression to Reverse Polish Notation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Stack]
10	Basic Calculator.java	Hard	Java	[Binary Tree, Expression Tree, Math, Minimum Binary Tree, Stack]
11	Expression Tree Build.java	Hard	Java	[Binary Tree, Expression Tree, Minimum Binary Tree, Stack]
12	Longest Valid Parentheses.java	Hard	Java	[Coordinate DP, Stack, String]
13	Decode String.java	Medium	Java	[DFS, Divide and Conquer, Stack]
14	Flatten Nested List Iterator.java	Medium	Java	[Design, Stack]
15	Min Stack.java	Easy	Java	[Design, Stack]
16	Implement Queue using Stacks.java	Easy	Java	[Design, Stack]
17	Implement Stack using Queues.java	Easy	Java	[Design, Stack]
18	Remove Duplicate Letters.java	Hard	Java	[Greedy, Hash Table, Stack]
19	Next Greater Element I.java	Easy	Java	[Hash Table, Stack]
20	Binary Tree Inorder Traversal.java	Easy	Java	[Hash Table, Stack, Tree]
21	Convert Binary Search Tree to Sorted Doubly Linked List (extra space).java	Medium	Java	[Linked List, Stack, Tree]
22	Evaluate Reverse Polish Notation.java	Medium	Java	[Stack]
23	Implement Stack.java	Easy	Java	[Stack]
24	Exclusive Time of Functions.java	Medium	Java	[Stack]
25	Simplify Path.java	Medium	Java	[Stack, String]
26	Valid Parentheses.java	Easy	Java	[Stack, String]
27	Maximum Binary Tree.java	Medium	Java	[Stack, Tree]
28	Binary Tree Postorder Traversal.java	Medium	Java	[Stack, Tree, Two Stacks]
29	Backspace String Compare.java	Easy	Java	[Stack, Two Pointers]

Sort (22)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Number of Airplane in the sky.java	Medium	Java	[Array, Interval, PriorityQueue, Sort, Sweep Line]
1	Sort Colors.java	Medium	Java	[Array, Partition, Quick Sort, Sort, Two Pointers]
2	Insert Interval.java	Hard	Java	[Array, PriorityQueue, Sort]
3	Merge Intervals.java	Medium	Java	[Array, PriorityQueue, Sort, Sweep Line]
4	Partition Array.java	Medium	Java	[Array, Quick Sort, Sort, Two Pointers]
5	Wiggle Sort.java	Medium	Java	[Array, Sort]
6	The Smallest Difference.java	Medium	Java	[Array, Sort, Two Pointers]
7	Intersection of Two Arrays II.java	Easy	Java	[Binary Search, Hash Table, Sort, Two Pointers]
8	Intersection of Two Arrays.java	Easy	Java	[Binary Search, Hash Table, Sort, Two Pointers]
9	H-Index.java	Medium	Java	[Bucket Sort, Hash Table, Sort]
10	Sort List.java	Medium	Java	[Divide and Conquer, Linked List, Merge Sort, Sort]
11	Meeting Rooms II.java	Medium	Java	[Greedy, Heap, PriorityQueue, Sort, Sweep Line]
12	Valid Anagram.java	Easy	Java	[Hash Table, Sort]
13	Insertion Sort List.java	Medium	Java	[Linked List, Sort]
14	MergeSort.java	Medium	Java	[Merge Sort, Sort]
15	Sort Colors II.java	Medium	Java	[Partition, Quick Sort, Sort, Two Pointers]
16	Sort Letters by Case.java	Medium	Java	[Partition, Sort, String, Two Pointers]
17	Subarray Sum Closest.java	Medium	Java	[PreSum, PriorityQueue, Sort, Subarray]
18	Exam Room.java	Medium	Java	[PriorityQueue, Sort]
19	Meeting Rooms.java	Easy	Java	[PriorityQueue, Sort, Sweep Line]
20	QuickSort.java	Medium	Java	[Quick Sort, Sort]
21	Largest Number.java	Medium	Java	[Sort]

BST (22)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Max Sum of Rectangle No Larger Than K.java	Hard	Java	[Array, BST, Binary Search, DP, Queue, TreeSet]
1	K Empty Slots.java	Hard	Java	[Array, BST, TreeSet]
2	Insert Node in a Binary Search Tree .java	Easy	Java	[BST]
3	Minimum Absolute Difference in BST.java	Easy	Java	[BST]
4	Remove Node in Binary Search Tree.java	Hard	Java	[BST]
5	Zigzag Iterator.java	Medium	Java	[BST]
6	Contains Duplicate III.java	Medium	Java	[BST]
7	Count of Smaller Numbers After Self.java	Hard	Java	[BST, Binary Indexed Tree, Binary Search, Divide and Conquer, Segment Tree]
8	Closest Binary Search Tree Value.java	Easy	Java	[BST, Binary Search, Tree]
9	Search Range in Binary Search Tree .java	Medium	Java	[BST, Binary Tree]
10	Convert Sorted List to Binary Search Tree.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List]
11	Convert Binary Search Tree to Sorted Doubly Linked List.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List, Tree]
12	Validate Binary Search Tree.java	Medium	Java	[BST, DFS, Divide and Conquer, Tree]
13	Kth Smallest Element in a BST.java	Medium	Java	[BST, DFS, Stack, Tree]
14	Lowest Common Ancestor of a Binary Search Tree.java	Medium	Java	[BST, DFS, Tree]
15	Recover Binary Search Tree.java	Hard	Java	[BST, DFS, Tree]
16	Unique Binary Search Tree II.java	Medium	Java	[BST, DP, Divide and Conquer, Tree]
17	Unique Binary Search Tree.java	Medium	Java	[BST, DP, Tree]
18	Binary Search Tree Iterator.java	Medium	Java	[BST, Design, Stack, Tree]
19	Count of Range Sum.java	Hard	Java	[BST, Divide and Conquer, Merge Sort, PreSum]
20	Trim a Binary Search Tree.java	Easy	Java	[BST, Tree]
21	Inorder Successor in BST.java	Medium	Java	[BST, Tree]

Design (21)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Insert Delete GetRandom O(1).java	Medium	Java	[Array, Design, Hash Table]
1	Serialize and Deserialize Binary Tree.java	Hard	Java	[BFS, DFS, Deque, Design, Divide and Conquer, Tree]
2	Binary Search Tree Iterator.java	Medium	Java	[BST, Design, Stack, Tree]
3	Add and Search Word - Data structure design.java	Medium	Java	[Backtracking, Design, Trie]
4	Singleton.java	Easy	Java	[Design]
5	Peeking Iterator.java	Medium	Java	[Design]
6	Flatten 2D Vector.java	Medium	Java	[Design]
7	Perfect Rectangle.java	Hard	Java	[Design, Geometry, Hash Table]
8	LFU Cache.java	Hard	Java	[Design, Hash Table]
9	Unique Word Abbreviation.java	Medium	Java	[Design, Hash Table]
10	ColorGrid.java	Medium	Java	[Design, Hash Table]
11	LRU Cache.java	Hard	Java	[Design, Hash Table, Linked List]
12	Design Search Autocomplete System.java	Hard	Java	[Design, Hash Table, MinHeap, PriorityQueue, Trie]
13	Find Median from Data Stream.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap]
14	Sliding Window Median.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap, Sliding Window]
15	Moving Average from Data Stream.java	Easy	Java	[Design, Queue, Sliding Window]
16	Flatten Nested List Iterator.java	Medium	Java	[Design, Stack]
17	Min Stack.java	Easy	Java	[Design, Stack]
18	Implement Queue using Stacks.java	Easy	Java	[Design, Stack]
19	Implement Stack using Queues.java	Easy	Java	[Design, Stack]
20	Implement Trie (Prefix Tree).java	Medium	Java	[Design, Trie]

Sequence DP (21)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Maximum Subarray.java	Easy	Java	[Array, DFS, DP, Divide and Conquer, PreSum, Sequence DP, Subarray]
1	Maximum Subarray II.java	Medium	Java	[Array, DP, Greedy, PreSum, Sequence DP, Subarray]
2	Best Time to Buy and Sell Stock II.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Status DP]
3	Best Time to Buy and Sell Stock with Transaction Fee.java	Medium	Java	[Array, DP, Greedy, Sequence DP, Status DP]
4	Minimum Subarray.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Subarray]
5	Best Time to Buy and Sell Stock III.java	Hard	Java	[Array, DP, Sequence DP]
6	Best Time to Buy and Sell Stock.java	Easy	Java	[Array, DP, Sequence DP]
7	Wildcard Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Greedy, Sequence DP, String]
8	Regular Expression Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Sequence DP, String]
9	Longest Common Subsequence.java	Medium	Java	[DP, Double Sequence DP, Sequence DP]
10	Edit Distance.java	Hard	Java	[DP, Double Sequence DP, Sequence DP, String]
11	Longest Common Substring.java	Medium	Java	[DP, Double Sequence DP, Sequence DP, String]
12	K Edit Distance.java	Hard	Java	[DP, Double Sequence DP, Sequence DP, Trie]
13	Word Break.java	Medium	Java	[DP, Hash Table, Sequence DP]
14	Climbing Stairs.java	Easy	Java	[DP, Memoization, Sequence DP]
15	House Robber.java	Easy	Java	[DP, Sequence DP]
16	Best Time to Buy and Sell Stock IV.java	Hard	Java	[DP, Sequence DP]
17	Paint Fence.java	Easy	Java	[DP, Sequence DP]
18	Paint House.java	Easy	Java	[DP, Sequence DP, Status DP]
19	House Robber II.java	Medium	Java	[DP, Sequence DP, Status DP]
20	Paint House II.java	Hard	Java	[DP, Sequence DP, Status DP]

PriorityQueue (19)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Task Scheduler.java	Medium	Java	[Array, Enumeration, Greedy, PriorityQueue, Queue]
1	Number of Airplane in the sky.java	Medium	Java	[Array, Interval, PriorityQueue, Sort, Sweep Line]
2	Insert Interval.java	Hard	Java	[Array, PriorityQueue, Sort]
3	Merge Intervals.java	Medium	Java	[Array, PriorityQueue, Sort, Sweep Line]
4	The Maze II.java	Medium	Java	[BFS, DFS, PriorityQueue]
5	The Maze III.java	Hard	Java	[BFS, DFS, PriorityQueue]
6	Trapping Rain Water II.java	Hard	Java	[BFS, Heap, MinHeap, PriorityQueue]
7	The Skyline Problem.java	Review	Java	[Binary Indexed Tree, Divide and Conquer, Heap, PriorityQueue, Segment Tree, Sweep Line]
8	Ugly Number II.java	Medium	Java	[DP, Enumeration, Heap, Math, PriorityQueue]
9	Design Search Autocomplete System.java	Hard	Java	[Design, Hash Table, MinHeap, PriorityQueue, Trie]
10	Merge k Sorted Lists.java	Medium	Java	[Divide and Conquer, Heap, Linked List, PriorityQueue]
11	Kth Largest Element in an Array.java	Medium	Java	[Divide and Conquer, Heap, MinHeap, PriorityQueue, Quick Sort]
12	Meeting Rooms II.java	Medium	Java	[Greedy, Heap, PriorityQueue, Sort, Sweep Line]
13	Top K Frequent Elements.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue]
14	Top K Frequent Words.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue, Trie]
15	Merge k Sorted Arrays.java	Medium	Java	[Heap, MinHeap, PriorityQueue]
16	Subarray Sum Closest.java	Medium	Java	[PreSum, PriorityQueue, Sort, Subarray]
17	Exam Room.java	Medium	Java	[PriorityQueue, Sort]
18	Meeting Rooms.java	Easy	Java	[PriorityQueue, Sort, Sweep Line]

Greedy (18)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Jump Game II.java	Hard	Java	[Array, Coordinate DP, DP, Greedy]
1	Jump Game.java	Medium	Java	[Array, DP, Greedy]
2	Maximum Subarray II.java	Medium	Java	[Array, DP, Greedy, PreSum, Sequence DP, Subarray]
3	Best Time to Buy and Sell Stock II.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Status DP]
4	Best Time to Buy and Sell Stock with Transaction Fee.java	Medium	Java	[Array, DP, Greedy, Sequence DP, Status DP]
5	Minimum Subarray.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Subarray]
6	Task Scheduler.java	Medium	Java	[Array, Enumeration, Greedy, PriorityQueue, Queue]
7	Find the Celebrity.java	Medium	Java	[Array, Greedy]
8	Wildcard Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Greedy, Sequence DP, String]
9	Cracking the Safe.java	Hard	Java	[DFS, Greedy, Math]
10	Coins in a Line.java	Medium	Java	[DP, Game Theory, Greedy]
11	Majority Number II.java	Medium	Java	[Enumeration, Greedy]
12	Queue Reconstruction by Height.java	Medium	Java	[Greedy]
13	Gas Station.java	Medium	Java	[Greedy]
14	Rearrange String k Distance Apart.java	Hard	Java	[Greedy, Hash Table, Heap]
15	Remove Duplicate Letters.java	Hard	Java	[Greedy, Hash Table, Stack]
16	Meeting Rooms II.java	Medium	Java	[Greedy, Heap, PriorityQueue, Sort, Sweep Line]
17	Delete Digits.java	Medium	Java	[Greedy, Priority Queue]

Bit Manipulation (17)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Subsets.java	Medium	Java	[Array, BFS, Backtracking, Bit Manipulation, DFS]
1	Majority Element.java	Easy	Java	[Array, Bit Manipulation, Divide and Conquer]
2	Missing Number.java	Easy	Java	[Array, Bit Manipulation, Math]
3	O(1) Check Power of 2.java	Easy	Java	[Bit Manipulation]
4	Single Number II.java	Medium	Java	[Bit Manipulation]
5	Single Number III.java	Medium	Java	[Bit Manipulation]
6	Sum of Two Integers.java	Easy	Java	[Bit Manipulation]
7	Swap Bits.java	Easy	Java	[Bit Manipulation]
8	Update Bits.java	Medium	Java	[Bit Manipulation]
9	Convert Integer A to Integer B.java	Easy	Java	[Bit Manipulation]
10	Count 1 in Binary.java	Easy	Java	[Bit Manipulation]
11	Total Hamming Distance.java	Medium	Java	[Bit Manipulation]
12	Binary Gap.java	Easy	Java	[Bit Manipulation]
13	Counting Bits.java	Medium	Java	[Bit Manipulation, Bitwise DP, DP]
14	Power of Two.java	Easy	Java	[Bit Manipulation, Math]
15	Binary Representation.java	Hard	Java	[Bit Manipulation, String]
16	Maximum XOR of Two Numbers in an Array.java	Medium	Java	[Bit Manipulation, Trie]

Coordinate DP (17)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Triangles.java	Medium	Java	[Array, Coordinate DP, DFS, DP, Memoization]
1	Unique Paths II.java	Medium	Java	[Array, Coordinate DP, DP]
2	Unique Path.java	Medium	Java	[Array, Coordinate DP, DP]
3	Longest Continuous Increasing Subsequence.java	Easy	Java	[Array, Coordinate DP, DP]
4	Minimum Path Sum.java	Medium	Java	[Array, Coordinate DP, DP]
5	Longest Increasing Continuous subsequence.java	Easy	Java	[Array, Coordinate DP, DP]
6	Jump Game II.java	Hard	Java	[Array, Coordinate DP, DP, Greedy]
7	Longest Increasing Continuous subsequence II.java	Medium	Java	[Array, Coordinate DP, DP, Memoization]
8	Russian Doll Envelopes.java	Hard	Java	[Binary Search, Coordinate DP, DP]
9	Longest Increasing Subsequence.java	Medium	Java	[Binary Search, Coordinate DP, DP, Memoization]
10	Longest Increasing Path in a Matrix.java	Hard	Java	[Coordinate DP, DFS, DP, Memoization, Topological Sort]
11	Bomb Enemy.java	Medium	Java	[Coordinate DP, DP]
12	Maximal Square.java	Medium	Java	[Coordinate DP, DP]
13	Number of Longest Increasing Subsequence.java	Medium	Java	[Coordinate DP, DP]
14	Continuous Subarray Sum.java	Medium	Java	[Coordinate DP, DP, Math, Subarray]
15	Minimum Swaps To Make Sequences Increasing.java	Medium	Java	[Coordinate DP, DP, Status DP]
16	Longest Valid Parentheses.java	Hard	Java	[Coordinate DP, Stack, String]

Heap (16)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Trapping Rain Water II.java	Hard	Java	[BFS, Heap, MinHeap, PriorityQueue]
1	The Skyline Problem.java	Review	Java	[Binary Indexed Tree, Divide and Conquer, Heap, PriorityQueue, Segment Tree, Sweep Line]
2	Kth Smallest Element in a Sorted Matrix.java	Medium	Java	[Binary Search, Heap]
3	Ugly Number II.java	Medium	Java	[DP, Enumeration, Heap, Math, PriorityQueue]
4	Sliding Window Maximum.java	Hard	Java	[Deque, Heap, Sliding Window]
5	Find Median from Data Stream.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap]
6	Sliding Window Median.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap, Sliding Window]
7	Merge k Sorted Lists.java	Medium	Java	[Divide and Conquer, Heap, Linked List, PriorityQueue]
8	Kth Largest Element in an Array.java	Medium	Java	[Divide and Conquer, Heap, MinHeap, PriorityQueue, Quick Sort]
9	Rearrange String k Distance Apart.java	Hard	Java	[Greedy, Hash Table, Heap]
10	Meeting Rooms II.java	Medium	Java	[Greedy, Heap, PriorityQueue, Sort, Sweep Line]
11	Top K Frequent Elements.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue]
12	Top K Frequent Words.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue, Trie]
13	HashHeap.java	Hard	Java	[HashHeap, Heap]
14	Heapify.java	Medium	Java	[Heap, MinHeap]
15	Merge k Sorted Arrays.java	Medium	Java	[Heap, MinHeap, PriorityQueue]

Union Find (15)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Longest Consecutive Sequence.java	Hard	Java	[Array, Hash Table, Union Find]
1	Redundant Connection.java	Medium	Java	[BFS, DFS, Graph, Tree, Union Find]
2	Evaluate Division.java	Medium	Java	[BFS, DFS, Graph, Union Find]
3	Number of Connected Components in an Undirected Graph.java	Medium	Java	[BFS, DFS, Graph, Union Find]
4	Graph Valid Tree.java	Medium	Java	[BFS, DFS, Graph, Union Find]
5	Number of Islands.java	Medium	Java	[BFS, DFS, Matrix DFS, Union Find]
6	Surrounded Regions.java	Medium	Java	[BFS, DFS, Matrix DFS, Union Find]
7	Redundant Connection II.java	Hard	Java	[DFS, Graph, Tree, Union Find]
8	Accounts Merge.java	Medium	Java	[DFS, Hash Table, Hash Table, Union Find]
9	Connecting Graph.java	Medium	Java	[Union Find]
10	Connecting Graph II.java	Medium	Java	[Union Find]
11	Connecting Graph III.java	Medium	Java	[Union Find]
12	Number of Islands II.java	Hard	Java	[Union Find]
13	Find the Weak Connected Component in the Directed Graph.java	Medium	Java	[Union Find]
14	Bricks Falling When Hit.java	Hard	Java	[Union Find]

Enumeration (15)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Rotate Image.java	Medium	Java	[Array, Enumeration]
1	Spiral Matrix.java	Medium	Java	[Array, Enumeration]
2	Task Scheduler.java	Medium	Java	[Array, Enumeration, Greedy, PriorityQueue, Queue]
3	Next Closest Time.java	Medium	Java	[Basic Implementation, Enumeration, String]
4	Strobogrammatic Number II.java	Medium	Java	[DFS, Enumeration, Math, Sequence DFS]
5	Ugly Number II.java	Medium	Java	[DP, Enumeration, Heap, Math, PriorityQueue]
6	Decode Ways II.java	Hard	Java	[DP, Enumeration, Partition DP]
7	Majority Number II.java	Medium	Java	[Enumeration, Greedy]
8	Valid Sudoku.java	Easy	Java	[Enumeration, Hash Table]
9	Strobogrammatic Number.java	Easy	Java	[Enumeration, Hash Table, Math]
10	Valid Number.java	Hard	Java	[Enumeration, Math, String]
11	Integer to English Words.java	Hard	Java	[Enumeration, Math, String]
12	Read N Characters Given Read4.java	Easy	Java	[Enumeration, String]
13	Text Justification.java	Hard	Java	[Enumeration, String]
14	Read N Characters Given Read4 II - Call multiple times.java	Hard	Java	[Enumeration, String]

Binary Tree (13)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Search Range in Binary Search Tree .java	Medium	Java	[BST, Binary Tree]
1	Binary Tree Paths.java	Easy	Java	[Backtracking, Binary Tree, DFS]
2	Flatten Binary Tree to Linked List.java	Medium	Java	[Binary Tree, DFS]
3	Segment Tree Query.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
4	Segment Tree Modify.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
5	Segment Tree Query II.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
6	Expression Evaluation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Minimum Binary Tree, Stack]
7	Convert Expression to Polish Notation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Stack]
8	Convert Expression to Reverse Polish Notation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Stack]
9	Segment Tree Build.java	Medium	Java	[Binary Tree, Divide and Conquer, Lint, Segment Tree]
10	Segment Tree Build II.java	Medium	Java	[Binary Tree, Divide and Conquer, Lint, Segment Tree]
11	Basic Calculator.java	Hard	Java	[Binary Tree, Expression Tree, Math, Minimum Binary Tree, Stack]
12	Expression Tree Build.java	Hard	Java	[Binary Tree, Expression Tree, Minimum Binary Tree, Stack]

Segment Tree (12)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Count of Smaller Numbers After Self.java	Hard	Java	[BST, Binary Indexed Tree, Binary Search, Divide and Conquer, Segment Tree]
1	Reverse Pairs.java	Medium	Java	[Binary Indexed Tree, Binary Search Tree, Divide and Conquer, Merge Sort, Segment Tree]
2	The Skyline Problem.java	Review	Java	[Binary Indexed Tree, Divide and Conquer, Heap, PriorityQueue, Segment Tree, Sweep Line]
3	Interval Minimum Number.java	Medium	Java	[Binary Search, Divide and Conquer, Lint, Segment Tree]
4	Interval Sum.java	Medium	Java	[Binary Search, Lint, Segment Tree]
5	Interval Sum II.java	Hard	Java	[Binary Search, Lint, Segment Tree]
6	Count of Smaller Number.java	Medium	Java	[Binary Search, Lint, Segment Tree]
7	Segment Tree Query.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
8	Segment Tree Modify.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
9	Segment Tree Query II.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
10	Segment Tree Build.java	Medium	Java	[Binary Tree, Divide and Conquer, Lint, Segment Tree]
11	Segment Tree Build II.java	Medium	Java	[Binary Tree, Divide and Conquer, Lint, Segment Tree]

Memoization (12)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Triangles.java	Medium	Java	[Array, Coordinate DP, DFS, DP, Memoization]
1	Longest Increasing Continuous subsequence II.java	Medium	Java	[Array, Coordinate DP, DP, Memoization]
2	Coins in a Line III.java	Hard	Java	[Array, DP, Game Theory, Interval DP, Memoization]
3	Coins in a Line II.java	Medium	Java	[Array, DP, Game Theory, Memoization, MiniMax]
4	Coin Change.java	Medium	Java	[Backpack DP, DP, Memoization]
5	Word Break II.java	Hard	Java	[Backtracking, DFS, DP, Hash Table, Memoization]
6	Longest Increasing Subsequence.java	Medium	Java	[Binary Search, Coordinate DP, DP, Memoization]
7	Longest Increasing Path in a Matrix.java	Hard	Java	[Coordinate DP, DFS, DP, Memoization, Topological Sort]
8	Longest Palindromic Subsequence.java	Medium	Java	[DFS, DP, Interval DP, Memoization]
9	Burst Balloons.java	Hard	Java	[DP, Divide and Conquer, Interval DP, Memoization]
10	Fibonacci.java	Easy	Java	[DP, Math, Memoization]
11	Climbing Stairs.java	Easy	Java	[DP, Memoization, Sequence DP]

Trie (11)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Word Search II.java	Hard	Java	[Backtracking, DFS, Trie]
1	Add and Search Word - Data structure design.java	Medium	Java	[Backtracking, Design, Trie]
2	Word Squares.java	Hard	Java	[Backtracking, Trie]
3	Maximum XOR of Two Numbers in an Array.java	Medium	Java	[Bit Manipulation, Trie]
4	K Edit Distance.java	Hard	Java	[DP, Double Sequence DP, Sequence DP, Trie]
5	Design Search Autocomplete System.java	Hard	Java	[Design, Hash Table, MinHeap, PriorityQueue, Trie]
6	Implement Trie (Prefix Tree).java	Medium	Java	[Design, Trie]
7	Top K Frequent Words.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue, Trie]
8	Palindrome Pairs.java	Hard	Java	[Hash Table, String, Trie]
9	Longest Word in Dictionary.java	Easy	Java	[Hash Table, Trie]
10	Prefix and Suffix Search.java	Hard	Java	[Trie]

Graph (11)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Course Schedule.java	Medium	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
1	Alien Dictionary.java	Hard	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
2	Clone Graph.java	Medium	Java	[BFS, DFS, Graph]
3	Course Schedule II.java	Medium	Java	[BFS, DFS, Graph, Topological Sort]
4	Redundant Connection.java	Medium	Java	[BFS, DFS, Graph, Tree, Union Find]
5	Evaluate Division.java	Medium	Java	[BFS, DFS, Graph, Union Find]
6	Number of Connected Components in an Undirected Graph.java	Medium	Java	[BFS, DFS, Graph, Union Find]
7	Graph Valid Tree.java	Medium	Java	[BFS, DFS, Graph, Union Find]
8	Minimum Height Trees.java	Medium	Java	[BFS, Graph]
9	Sliding Puzzle.java	Hard	Java	[BFS, Graph]
10	Redundant Connection II.java	Hard	Java	[DFS, Graph, Tree, Union Find]

Subarray (11)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Minimum Size Subarray Sum.java	Medium	Java	[Array, Binary Search, Subarray, Two Pointers]
1	Maximum Subarray.java	Easy	Java	[Array, DFS, DP, Divide and Conquer, PreSum, Sequence DP, Subarray]
2	Maximum Subarray II.java	Medium	Java	[Array, DP, Greedy, PreSum, Sequence DP, Subarray]
3	Minimum Subarray.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Subarray]
4	Maximum Product Subarray.java	Medium	Java	[Array, DP, Subarray]
5	Subarray Sum.java	Easy	Java	[Array, Hash Table, PreSum, Subarray]
6	Subarray Sum Equals K.java	Medium	Java	[Array, Hash Table, PreSum, Subarray]
7	Maximum Average Subarray I.java	Easy	Java	[Array, Subarray]
8	Continuous Subarray Sum.java	Medium	Java	[Coordinate DP, DP, Math, Subarray]
9	Maximum Size Subarray Sum Equals k.java	Medium	Java	[Hash Table, PreSum, Subarray]
10	Subarray Sum Closest.java	Medium	Java	[PreSum, PriorityQueue, Sort, Subarray]

PreSum (10)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Maximum Average Subarray II.java	Review	Java	[Array, Binary Search, PreSum]
1	Maximum Subarray.java	Easy	Java	[Array, DFS, DP, Divide and Conquer, PreSum, Sequence DP, Subarray]
2	Maximum Subarray II.java	Medium	Java	[Array, DP, Greedy, PreSum, Sequence DP, Subarray]
3	Submatrix Sum.java	Medium	Java	[Array, Hash Table, PreSum]
4	Subarray Sum.java	Easy	Java	[Array, Hash Table, PreSum, Subarray]
5	Subarray Sum Equals K.java	Medium	Java	[Array, Hash Table, PreSum, Subarray]
6	Count of Range Sum.java	Hard	Java	[BST, Divide and Conquer, Merge Sort, PreSum]
7	Range Sum Query - Immutable.java	Easy	Java	[DP, PreSum]
8	Maximum Size Subarray Sum Equals k.java	Medium	Java	[Hash Table, PreSum, Subarray]
9	Subarray Sum Closest.java	Medium	Java	[PreSum, PriorityQueue, Sort, Subarray]

Lint (9)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Interval Minimum Number.java	Medium	Java	[Binary Search, Divide and Conquer, Lint, Segment Tree]
1	Interval Sum.java	Medium	Java	[Binary Search, Lint, Segment Tree]
2	Interval Sum II.java	Hard	Java	[Binary Search, Lint, Segment Tree]
3	Count of Smaller Number.java	Medium	Java	[Binary Search, Lint, Segment Tree]
4	Segment Tree Query.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
5	Segment Tree Modify.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
6	Segment Tree Query II.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
7	Segment Tree Build.java	Medium	Java	[Binary Tree, Divide and Conquer, Lint, Segment Tree]
8	Segment Tree Build II.java	Medium	Java	[Binary Tree, Divide and Conquer, Lint, Segment Tree]

MinHeap (9)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Trapping Rain Water II.java	Hard	Java	[BFS, Heap, MinHeap, PriorityQueue]
1	Design Search Autocomplete System.java	Hard	Java	[Design, Hash Table, MinHeap, PriorityQueue, Trie]
2	Find Median from Data Stream.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap]
3	Sliding Window Median.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap, Sliding Window]
4	Kth Largest Element in an Array.java	Medium	Java	[Divide and Conquer, Heap, MinHeap, PriorityQueue, Quick Sort]
5	Top K Frequent Elements.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue]
6	Top K Frequent Words.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue, Trie]
7	Heapify.java	Medium	Java	[Heap, MinHeap]
8	Merge k Sorted Arrays.java	Medium	Java	[Heap, MinHeap, PriorityQueue]

Backpack DP (8)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Combination Sum IV.java	Medium	Java	[Array, Backpack DP, DP]
1	Backpack VI.java	Medium	Java	[Backpack DP, DP]
2	Coin Change 2.java	Medium	Java	[Backpack DP, DP]
3	Backpack.java	Medium	Java	[Backpack DP, DP]
4	Backpack II.java	Medium	Java	[Backpack DP, DP]
5	Backpack V.java	Medium	Java	[Backpack DP, DP]
6	Backpack III.java	Hard	Java	[Backpack DP, DP]
7	Coin Change.java	Medium	Java	[Backpack DP, DP, Memoization]

Status DP (7)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Best Time to Buy and Sell Stock II.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Status DP]
1	Best Time to Buy and Sell Stock with Transaction Fee.java	Medium	Java	[Array, DP, Greedy, Sequence DP, Status DP]
2	Minimum Swaps To Make Sequences Increasing.java	Medium	Java	[Coordinate DP, DP, Status DP]
3	House Robber III.java	Medium	Java	[DFS, DP, Status DP, Tree]
4	Paint House.java	Easy	Java	[DP, Sequence DP, Status DP]
5	House Robber II.java	Medium	Java	[DP, Sequence DP, Status DP]
6	Paint House II.java	Hard	Java	[DP, Sequence DP, Status DP]

Double Sequence DP (6)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Wildcard Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Greedy, Sequence DP, String]
1	Regular Expression Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Sequence DP, String]
2	Longest Common Subsequence.java	Medium	Java	[DP, Double Sequence DP, Sequence DP]
3	Edit Distance.java	Hard	Java	[DP, Double Sequence DP, Sequence DP, String]
4	Longest Common Substring.java	Medium	Java	[DP, Double Sequence DP, Sequence DP, String]
5	K Edit Distance.java	Hard	Java	[DP, Double Sequence DP, Sequence DP, Trie]

Sliding Window (6)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Sliding Window Maximum.java	Hard	Java	[Deque, Heap, Sliding Window]
1	Sliding Window Median.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap, Sliding Window]
2	Moving Average from Data Stream.java	Easy	Java	[Design, Queue, Sliding Window]
3	Find All Anagrams in a String.java	Easy	Java	[Hash Table, Sliding Window]
4	Longest Substring with At Most K Distinct Characters.java	Hard	Java	[Hash Table, Sliding Window, String]
5	Longest Substring with At Most Two Distinct Characters.java	Hard	Java	[Hash Table, Sliding Window, String, Two Pointers]

Quick Sort (6)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Sort Colors.java	Medium	Java	[Array, Partition, Quick Sort, Sort, Two Pointers]
1	Median.java	Easy	Java	[Array, Quick Select, Quick Sort]
2	Partition Array.java	Medium	Java	[Array, Quick Sort, Sort, Two Pointers]
3	Kth Largest Element in an Array.java	Medium	Java	[Divide and Conquer, Heap, MinHeap, PriorityQueue, Quick Sort]
4	Sort Colors II.java	Medium	Java	[Partition, Quick Sort, Sort, Two Pointers]
5	QuickSort.java	Medium	Java	[Quick Sort, Sort]

Partition DP (5)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Perfect Squares.java	Medium	Java	[BFS, DP, Math, Partition DP]
1	Copy Books.java	Hard	Java	[Binary Search, DP, Partition DP]
2	Decode Ways II.java	Hard	Java	[DP, Enumeration, Partition DP]
3	Palindrome Partitioning II.java	Hard	Java	[DP, Partition DP]
4	Decode Ways.java	Medium	Java	[DP, Partition DP, String]

Sweep Line (5)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Number of Airplane in the sky.java	Medium	Java	[Array, Interval, PriorityQueue, Sort, Sweep Line]
1	Merge Intervals.java	Medium	Java	[Array, PriorityQueue, Sort, Sweep Line]
2	The Skyline Problem.java	Review	Java	[Binary Indexed Tree, Divide and Conquer, Heap, PriorityQueue, Segment Tree, Sweep Line]
3	Meeting Rooms II.java	Medium	Java	[Greedy, Heap, PriorityQueue, Sort, Sweep Line]
4	Meeting Rooms.java	Easy	Java	[PriorityQueue, Sort, Sweep Line]

Topological Sort (5)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Course Schedule.java	Medium	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
1	Alien Dictionary.java	Hard	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
2	Course Schedule II.java	Medium	Java	[BFS, DFS, Graph, Topological Sort]
3	Topological Sorting.java	Medium	Java	[BFS, DFS, Topological Sort]
4	Longest Increasing Path in a Matrix.java	Hard	Java	[Coordinate DP, DFS, DP, Memoization, Topological Sort]

Expression Tree (5)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Expression Evaluation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Minimum Binary Tree, Stack]
1	Convert Expression to Polish Notation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Stack]
2	Convert Expression to Reverse Polish Notation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Stack]
3	Basic Calculator.java	Hard	Java	[Binary Tree, Expression Tree, Math, Minimum Binary Tree, Stack]
4	Expression Tree Build.java	Hard	Java	[Binary Tree, Expression Tree, Minimum Binary Tree, Stack]

Merge Sort (4)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Count of Range Sum.java	Hard	Java	[BST, Divide and Conquer, Merge Sort, PreSum]
1	Reverse Pairs.java	Medium	Java	[Binary Indexed Tree, Binary Search Tree, Divide and Conquer, Merge Sort, Segment Tree]
2	Sort List.java	Medium	Java	[Divide and Conquer, Linked List, Merge Sort, Sort]
3	MergeSort.java	Medium	Java	[Merge Sort, Sort]

Game Theory (4)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Coins in a Line III.java	Hard	Java	[Array, DP, Game Theory, Interval DP, Memoization]
1	Coins in a Line II.java	Medium	Java	[Array, DP, Game Theory, Memoization, MiniMax]
2	Nim Game.java	Easy	Java	[Brainteaser, DP, Game Theory]
3	Coins in a Line.java	Medium	Java	[DP, Game Theory, Greedy]

Combination (4)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Combination Sum.java	Medium	Java	[Array, Backtracking, Combination, DFS]
1	Combination Sum II.java	Medium	Java	[Array, Backtracking, Combination, DFS]
2	Combination Sum III.java	Medium	Java	[Array, Backtracking, Combination, DFS]
3	Combinations.java	Medium	Java	[Backtracking, Combination, DFS]

Interval DP (4)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Coins in a Line III.java	Hard	Java	[Array, DP, Game Theory, Interval DP, Memoization]
1	Longest Palindromic Subsequence.java	Medium	Java	[DFS, DP, Interval DP, Memoization]
2	Burst Balloons.java	Hard	Java	[DP, Divide and Conquer, Interval DP, Memoization]
3	Scramble String.java	Hard	Java	[DP, Interval DP, String]

MaxHeap (4)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Find Median from Data Stream.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap]
1	Sliding Window Median.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap, Sliding Window]
2	Top K Frequent Elements.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue]
3	Top K Frequent Words.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue, Trie]

Permutation (3)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Permutations.java	Medium	Java	[Backtracking, DFS, Permutation]
1	Palindrome Permutation II.java	Medium	Java	[Backtracking, Permutation]
2	Shuffle an Array.java	Medium	Java	[Permutation]

Binary Indexed Tree (3)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Count of Smaller Numbers After Self.java	Hard	Java	[BST, Binary Indexed Tree, Binary Search, Divide and Conquer, Segment Tree]
1	Reverse Pairs.java	Medium	Java	[Binary Indexed Tree, Binary Search Tree, Divide and Conquer, Merge Sort, Segment Tree]
2	The Skyline Problem.java	Review	Java	[Binary Indexed Tree, Divide and Conquer, Heap, PriorityQueue, Segment Tree, Sweep Line]

Minimum Binary Tree (3)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Expression Evaluation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Minimum Binary Tree, Stack]
1	Basic Calculator.java	Hard	Java	[Binary Tree, Expression Tree, Math, Minimum Binary Tree, Stack]
2	Expression Tree Build.java	Hard	Java	[Binary Tree, Expression Tree, Minimum Binary Tree, Stack]

Basic Implementation (3)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Cosine Similarity.java	Easy	Java	[Basic Implementation]
1	Next Closest Time.java	Medium	Java	[Basic Implementation, Enumeration, String]
2	Count and Say.java	Easy	Java	[Basic Implementation, String]

Queue (3)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Max Sum of Rectangle No Larger Than K.java	Hard	Java	[Array, BST, Binary Search, DP, Queue, TreeSet]
1	Task Scheduler.java	Medium	Java	[Array, Enumeration, Greedy, PriorityQueue, Queue]
2	Moving Average from Data Stream.java	Easy	Java	[Design, Queue, Sliding Window]

Partition (3)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Sort Colors.java	Medium	Java	[Array, Partition, Quick Sort, Sort, Two Pointers]
1	Sort Colors II.java	Medium	Java	[Partition, Quick Sort, Sort, Two Pointers]
2	Sort Letters by Case.java	Medium	Java	[Partition, Sort, String, Two Pointers]

Sequence DFS (2)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Generate Parentheses.java	Medium	Java	[Backtracking, DFS, Sequence DFS, String]
1	Strobogrammatic Number II.java	Medium	Java	[DFS, Enumeration, Math, Sequence DFS]

Double Recursive (2)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Binary Tree Longest Consecutive Sequence II.java	Medium	Java	[DFS, Divide and Conquer, Double Recursive, Tree]
1	Path Sum III.java	Easy	Java	[DFS, Double Recursive, Tree]

TreeSet (2)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Max Sum of Rectangle No Larger Than K.java	Hard	Java	[Array, BST, Binary Search, DP, Queue, TreeSet]
1	K Empty Slots.java	Hard	Java	[Array, BST, TreeSet]

Matrix DFS (2)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Number of Islands.java	Medium	Java	[BFS, DFS, Matrix DFS, Union Find]
1	Surrounded Regions.java	Medium	Java	[BFS, DFS, Matrix DFS, Union Find]

MiniMax (2)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Coins in a Line II.java	Medium	Java	[Array, DP, Game Theory, Memoization, MiniMax]
1	Predict the Winner.java	Medium	Java	[DP, MiniMax]

Deque (2)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Serialize and Deserialize Binary Tree.java	Hard	Java	[BFS, DFS, Deque, Design, Divide and Conquer, Tree]
1	Sliding Window Maximum.java	Hard	Java	[Deque, Heap, Sliding Window]

Geometry (2)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Max Points on a Line.java	Hard	Java	[Array, Geometry, Hash Table, Math]
1	Perfect Rectangle.java	Hard	Java	[Design, Geometry, Hash Table]

Priority Queue (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Delete Digits.java	Medium	Java	[Greedy, Priority Queue]

HashHeap (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	HashHeap.java	Hard	Java	[HashHeap, Heap]

Binary Search Tree (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Reverse Pairs.java	Medium	Java	[Binary Indexed Tree, Binary Search Tree, Divide and Conquer, Merge Sort, Segment Tree]

KMP (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Shortest Palindrome.java	Hard	Java	[KMP, String]

Brainteaser (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Nim Game.java	Easy	Java	[Brainteaser, DP, Game Theory]

Interval (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Number of Airplane in the sky.java	Medium	Java	[Array, Interval, PriorityQueue, Sort, Sweep Line]

Bitwise DP (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Counting Bits.java	Medium	Java	[Bit Manipulation, Bitwise DP, DP]

Quick Select (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Median.java	Easy	Java	[Array, Quick Select, Quick Sort]

Bucket Sort (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	H-Index.java	Medium	Java	[Bucket Sort, Hash Table, Sort]

Monotonous Stack (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Largest Rectangle in Histogram.java	Hard	Java	[Array, Monotonous Stack, Stack]

PreProduct (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Product of Array Except Self.java	Medium	Java	[Array, PreProduct]

Reservior Sampling (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Random Pick Index.java	Medium	Java	[Reservior Sampling]

TreeMap (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	My Calendar I.java	Medium	Java	[Array, TreeMap]

Two Stacks (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Binary Tree Postorder Traversal.java	Medium	Java	[Stack, Tree, Two Stacks]

Tree DP (1)

Squence	Problem	Level	Language	Tags	Video Tutorial
0	Binary Tree Maximum Path Sum.java	Hard	Java	[DFS, DP, Tree, Tree DP]