题解 | #二叉搜索树的第k个节点#

import java.util.*;

/*

• public class TreeNode {
• int val = 0;
• TreeNode left = null;
• TreeNode right = null;
• public TreeNode(int val) {

• this.val = val;
  

• }
• } */

public class Solution { /** * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可 * * * @param proot TreeNode类 * @param k int整型 * @return int整型 */ private List inOrderSet = new ArrayList<>(); public int KthNode (TreeNode proot, int k) { if(proot == null || k == 0){ return -1; } inOrder(proot); if(k > inOrderSet.size()){ return -1; } return inOrderSet.get(k - 1); // write code here } public void inOrder(TreeNode root){ if(root == null){ return; } inOrder(root.left); inOrderSet.add(root.val); inOrder(root.right); } }