题解 | #二叉搜索树的第k个结点# 减法求解

public class Solution {
    private TreeNode res;
    private int idx;
    TreeNode KthNode(TreeNode pRoot, int k) {
        idx=k;
        dfs(pRoot);
        return res;
    }

    private void dfs(TreeNode node){
        if(node==null) return;
        dfs(node.left);
        if(idx==0) return;
        if(--idx==0) res = node;
        dfs(node.right);
    }
}