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 res=-1, count=0;
    public int KthNode (TreeNode proot, int k) {
        recur(proot, k);        
        return res;
    }
    public void recur(TreeNode proot, int k) {
        if(proot == null || count==k) return ;
        recur(proot.left, k);
        count++;
        if(k==count) {
            res = proot.val;
        }
        recur(proot.right, k);
    }
}