Leetcode 145.binary tree postorder traversal

原题地址：https://leetcode.com/problems/binary-tree-postorder-traversal/description/

题目描述

Given a binary tree, return the postorder traversal of its nodes' values.

后续遍历二叉树

思路

递归写法和非递归写法。难度设置成Hard应该要写非递归的比较合理一些，不过暂时不会…先写个递归的凑数

代码

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> result;
    vector<int> postorderTraversal(TreeNode* root) {
        if(root==NULL){
            
        }else{
            postorderTraversal(root->left);
            postorderTraversal(root->right);
            result.push_back(root->val);
        }
        return result;
    }
};