0530._Minimum_Absolute_Difference_in_BST.md

530. Minimum Absolute Difference in BST

难度: Easy

刷题内容

原题连接

• https://leetcode.com/problems/minimum-absolute-difference-in-bst/

内容描述

Given a binary search tree with non-negative values, find the minimum absolute difference between values of any two nodes.

Example:

Input:

   1
    \
     3
    /
   2

Output:
1

Explanation:
The minimum absolute difference is 1, which is the difference between 2 and 1 (or between 2 and 3).
 

Note: There are at least two nodes in this BST.

解题方案

思路 1 - 时间复杂度: O(N)- 空间复杂度: O(N)******

inorder遍历BST已经有序，只需要算所有相邻两个数的差的绝对值就可以了，不需要两轮遍历

class Solution:
    def getMinimumDifference(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        vals = []
        def inorder(root):
            if not root:
                return
            inorder(root.left)
            vals.append(root.val)
            inorder(root.right)
        inorder(root)
        return min(abs(vals[i] - vals[i-1]) for i in range(1, len(vals))) # vals is already sorted in BST