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@CodersAcademy006
CodersAcademy006 authored Aug 10, 2024
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145 changes: 72 additions & 73 deletions solution/0000-0099/0001.Two Sum/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -70,11 +70,11 @@ tags:

### 方法一：哈希表

我们可以用哈希表 $m$ 存放数组值以及对应的下标。
我们可以使用一个哈希表 $\textit{d}$ 来存储每个元素及其对应的索引。

遍历数组 `nums`，当发现 `target - nums[i]` 在哈希表中，说明找到了目标值，返回 `target - nums[i]` 的下标以及 $i$ 即可。
遍历数组 $\textit{nums}$，对于当前元素 $\textit{nums}[i]$，我们首先判断 $\textit{target} - \textit{nums}[i]$ 是否在哈希表 $\textit{d}$ 中，如果在 $\textit{d}$ 中，说明 $\textit{target}$ 值已经找到，返回 $\textit{target} - \textit{nums}[i]$ 的索引和 $i$ 即可。

时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 是数组 `nums` 的长度。
时间复杂度 $O(n)$，空间复杂度 $O(n)$，其中 $n$ 为数组 $\textit{nums}$ 的长度。

<!-- tabs:start -->

Expand All @@ -83,27 +83,27 @@ tags:
```python
class Solution:
def twoSum(self, nums: List[int], target: int) -> List[int]:
m = {}
d = {}
for i, x in enumerate(nums):
y = target - x
if y in m:
return [m[y], i]
m[x] = i
if y in d:
return [d[y], i]
d[x] = i
```

#### Java

```java
class Solution {
public int[] twoSum(int[] nums, int target) {
Map<Integer, Integer> m = new HashMap<>();
Map<Integer, Integer> d = new HashMap<>();
for (int i = 0;; ++i) {
int x = nums[i];
int y = target - x;
if (m.containsKey(y)) {
return new int[] {m.get(y), i};
if (d.containsKey(y)) {
return new int[] {d.get(y), i};
}
m.put(x, i);
d.put(x, i);
}
}
}
Expand All @@ -115,14 +115,14 @@ class Solution {
class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
unordered_map<int, int> m;
unordered_map<int, int> d;
for (int i = 0;; ++i) {
int x = nums[i];
int y = target - x;
if (m.count(y)) {
return {m[y], i};
if (d.contains(y)) {
return {d[y], i};
}
m[x] = i;
d[x] = i;
}
}
};
Expand All @@ -132,14 +132,14 @@ public:
```go
func twoSum(nums []int, target int) []int {
m := map[int]int{}
d := map[int]int{}
for i := 0; ; i++ {
x := nums[i]
y := target - x
if j, ok := m[y]; ok {
if j, ok := d[y]; ok {
return []int{j, i}
}
m[x] = i
d[x] = i
}
}
```
Expand All @@ -148,17 +148,14 @@ func twoSum(nums []int, target int) []int {

```ts
function twoSum(nums: number[], target: number): number[] {
const m: Map<number, number> = new Map();

const d = new Map<number, number>();
for (let i = 0; ; ++i) {
const x = nums[i];
const y = target - x;

if (m.has(y)) {
return [m.get(y)!, i];
if (d.has(y)) {
return [d.get(y)!, i];
}

m.set(x, i);
d.set(x, i);
}
}
```
Expand All @@ -170,15 +167,15 @@ use std::collections::HashMap;

impl Solution {
pub fn two_sum(nums: Vec<i32>, target: i32) -> Vec<i32> {
let mut m = HashMap::new();
let mut d = HashMap::new();
for (i, &x) in nums.iter().enumerate() {
let y = target - x;
if let Some(&j) = m.get(&y) {
if let Some(&j) = d.get(&y) {
return vec![j as i32, i as i32];
}
m.insert(x, i as i32);
d.insert(x, i);
}
unreachable!()
vec![]
}
}
```
Expand All @@ -192,14 +189,14 @@ impl Solution {
* @return {number[]}
*/
var twoSum = function (nums, target) {
const m = new Map();
const d = new Map();
for (let i = 0; ; ++i) {
const x = nums[i];
const y = target - x;
if (m.has(y)) {
return [m.get(y), i];
if (d.has(y)) {
return [d.get(y), i];
}
m.set(x, i);
d.set(x, i);
}
};
```
Expand All @@ -209,15 +206,15 @@ var twoSum = function (nums, target) {
```cs
public class Solution {
public int[] TwoSum(int[] nums, int target) {
var m = new Dictionary<int, int>();
var d = new Dictionary<int, int>();
for (int i = 0, j; ; ++i) {
int x = nums[i];
int y = target - x;
if (m.TryGetValue(y, out j)) {
if (d.TryGetValue(y, out j)) {
return new [] {j, i};
}
if (!m.ContainsKey(x)) {
m.Add(x, i);
if (!d.ContainsKey(x)) {
d.Add(x, i);
}
}
}
Expand All @@ -234,13 +231,13 @@ class Solution {
* @return Integer[]
*/
function twoSum($nums, $target) {
$m = [];
$d = [];
foreach ($nums as $i => $x) {
$y = $target - $x;
if (isset($m[$y])) {
return [$m[$y], $i];
if (isset($d[$y])) {
return [$d[$y], $i];
}
$m[$x] = $i;
$d[$x] = $i;
}
}
}
Expand All @@ -252,17 +249,20 @@ class Solution {
import scala.collection.mutable

object Solution {
def twoSum(nums: Array[Int], target: Int): Array[Int] = {
var map = new mutable.HashMap[Int, Int]()
for (i <- 0 to nums.length) {
if (map.contains(target - nums(i))) {
return Array(map(target - nums(i)), i)
} else {
map += (nums(i) -> i)
}
def twoSum(nums: Array[Int], target: Int): Array[Int] = {
val d = mutable.Map[Int, Int]()
var ans: Array[Int] = Array()
for (i <- nums.indices if ans.isEmpty) {
val x = nums(i)
val y = target - x
if (d.contains(y)) {
ans = Array(d(y), i)
} else {
d(x) = i
}
}
ans
}
Array(0, 0)
}
}
```

Expand All @@ -271,17 +271,15 @@ object Solution {
```swift
class Solution {
func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
var m = [Int: Int]()
var i = 0
while true {
let x = nums[i]
let y = target - nums[i]
if let j = m[target - nums[i]] {
var d = [Int: Int]()
for (i, x) in nums.enumerated() {
let y = target - x
if let j = d[y] {
return [j, i]
}
m[nums[i]] = i
i += 1
d[x] = i
}
return []
}
}
```
Expand All @@ -293,30 +291,31 @@ class Solution {
# @param {Integer} target
# @return {Integer[]}
def two_sum(nums, target)
nums.each_with_index do |x, idx|
if nums.include? target - x
return [idx, nums.index(target - x)] if nums.index(target - x) != idx
d = {}
nums.each_with_index do |x, i|
y = target - x
if d.key?(y)
return [d[y], i]
end
d[x] = i
end
next
end
end
```

#### Nim

```nim
import std/enumerate
import std/tables
proc twoSum(nums: seq[int], target: int): seq[int] =
var
bal: int
tdx: int
for idx, val in enumerate(nums):
bal = target - val
if bal in nums:
tdx = nums.find(bal)
if idx != tdx:
return @[idx, tdx]
var d = initTable[int, int]()
for i, x in nums.pairs():
let y = target - x
if d.hasKey(y):
return @[d[y], i]
d[x] = i
return @[]
```

<!-- tabs:end -->
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