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
     */
    public int KthNode (TreeNode proot, int k) {

        Deque<TreeNode> stack = new ArrayDeque<>();
        if (null == proot || k == 0) return -1;

        int i = 0;

        while (proot != null || !stack.isEmpty()) {

            while (proot != null) {
                stack.push(proot);
                proot = proot.left;
            }
            // 打印左
            proot = stack.pop();
            i++;
            if (i == k) return proot.val;

            proot = proot.right;

        }
        return -1;
    }
}

使用基于迭代的中序遍历方式来获取