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
     */
    int ans = -1;
    int cnt = 0;
    public int KthNode (TreeNode proot, int k) {
        // write code here
        ans = -1;
        cnt = k;
        kFind(proot);
        return ans;
    }
    public void kFind(TreeNode root) {
        if(root == null) {
            return;
        }
        kFind(root.left);        
        cnt--;
        if(cnt == 0) {
            ans = root.val;
            return;
        }
        kFind(root.right);
    }
}