[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},

   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

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