力扣面试150题--二叉搜索树中第k小的元素

Day 58

题目描述

思路

直接采取中序遍历，不过我们将k参与到中序遍历中，遍历到第k个元素就结束

/*** Definition for a binary tree node.* public class TreeNode {*     int val;*     TreeNode left;*     TreeNode right;*     TreeNode() {}*     TreeNode(int val) { this.val = val; }*     TreeNode(int val, TreeNode left, TreeNode right) {*         this.val = val;*         this.left = left;*         this.right = right;*     }* }*/
class Solution {int x=1;int num;public void mid(TreeNode root,int k){if(root==null||x>k){return;}mid(root.left,k);if(x==k){num=root.val;}x++;mid(root.right,k);}public int kthSmallest(TreeNode root, int k) {mid(root,k);return num;}
}