[LeetCode]Binary Tree Postorder Traversal

Binary Tree Postorder Traversal

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

For example:
Given binary tree {1,#,2,3},

return [3,2,1].

Note: Recursive solution is trivial, could you do it iteratively?

迭代的方法略显复杂。

递归的方法很统一。先序，中序，后续，只要修改遍历的顺序即可。

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     vector<int> postorderTraversal(TreeNode* root) {
13         vector<int> result;
14         traversal(root,result);
15         return result;
16     }
17     void traversal(TreeNode* root,vector<int>& ret)
18     {
19         if(root)
20         {
21             traversal(root->left,ret);
22             traversal(root->right,ret);
23             ret.push_back(root->val);
24         }
25     }
26 };