根据二叉搜索的性质可知,中序遍历即位从小到大顺序,可以使用中序遍历将其存起来取出目标节点,也可直接中序遍历同时得到节点
/* public class TreeNode { int val = 0; TreeNode left = null; TreeNode right = null; public TreeNode(int val) { this.val = val; } } */ public class Solution { int index = 0; TreeNode res = null; TreeNode KthNode(TreeNode pRoot, int k) { if(pRoot==null||k == 0){ return null; } KthNode(pRoot.left,k); index++; if(index == k){ res = pRoot; } KthNode(pRoot.right,k); return res; } }