LeetCode 145 : Binary Tree Postorder Traversal

和先序遍历类似，根节点的操作放在最后间就可。

/**
 * 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> path;   
    vector<int> postorderTraversal(TreeNode* root) {
        if(root!=NULL){
			postorderTraversal(root->left);
			postorderTraversal(root->right);
			path.push_back(root->val);
		}
		return path;
    }
};