题解 | #二叉搜索树的第k个结点#

利用栈进行中序遍历

/*
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
import java.util.*;
public class Solution {
    TreeNode KthNode(TreeNode pRoot, int k) {
        if(pRoot == null || k==0){
            return null;
        }
        Stack<TreeNode> we = new Stack<>();
        
        while(true){
            if(pRoot!=null){
                we.push(pRoot);
                pRoot=pRoot.left;
                        
             }else{
                pRoot = we.pop();
                System.out.print(pRoot.val);
                if(--k == 0){
                    
                    return pRoot;
                }
                pRoot = pRoot.right;
            }
            if(we.isEmpty() && pRoot == null){
               // System.out.print(k);
                break;
            }
        }
        return null;
        
    }
    


}