原題地址：https://leetcode.com/problems/binary-tree-postorder-traversal/description/

題目描述

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

后續遍歷二叉樹

思路

遞歸寫法和非遞歸寫法。難度設置成Hard應該要寫非遞歸的比較合理一些，不過暫時不會…先寫個遞歸的湊數

代碼

/**
 * 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;
    }
};