题解 | #二叉搜索树的第k个节点#

非递归中序遍历，用一个计数器代表K，找到第K个就break

import java.util.*;


public class Solution {
   
    public int KthNode (TreeNode proot, int k) {
        // write code here
        if(proot == null){
            return -1;
        }
        
        Stack<TreeNode> s = new Stack<>();
        int n = 0;
        int res = -1;
        
        while(!s.isEmpty() ||  proot != null){
            if(proot != null){
                s.push(proot);
                proot = proot.left;
            } else {
                proot = s.pop();
                if(++n == k){
                    res = proot.val;
                    break;
                }
                proot = proot.right;
            }
        }
        return res;
    }
}