[LeetCode]Binary Tree Postorder Traversal

原题链接：http://oj.leetcode.com/problems/binary-tree-postorder-traversal/

题意描述：

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?

题解：

　　二叉树的后序遍历，我用的是递归，比较简洁。关于二叉树的基础，我之前有一个总结：http://www.cnblogs.com/codershell/p/3291601.html

 1 /**
 2  * Definition for binary tree
 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     void traversal(vector<int> &v,TreeNode* root){
13         if(root == NULL)
14             return;
15         
16         traversal(v,root->left);
17         traversal(v,root->right);
18         v.push_back(root->val);
19     }
20     vector<int> postorderTraversal(TreeNode *root) {
21         vector<int> v;
22         traversal(v,root);
23         return v;
24     }
25 };

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