Path Sum II

Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5
             / \
            4   8
           /   / \
          11  13  4
         /  \    / \
        7    2  5   1

return

[
   [5,4,11,2],
   [5,8,4,5]
]

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<vector<int> > pathSum(TreeNode *root, int sum) {
        vector<vector<int> > ans;
        vector<int> arr;
        if(root) iter(root, sum, 0, arr, ans);
        return ans;
    }
    void iter(TreeNode *root, int sum, int tmpsum, vector<int> arr, vector<vector<int> > &ans){
        if(root->left==NULL && root->right==NULL){
            tmpsum += root->val;
            if(tmpsum == sum){
                arr.push_back(root->val);
                ans.push_back(arr);
                return;
            }
            return;
        }
        vector<int> tmp(arr);
        tmp.push_back(root->val);
        tmpsum += root->val;

        if(root->left){
            iter(root->left, sum, tmpsum, tmp, ans);
        }
        if(root->right){
            iter(root->right, sum, tmpsum, tmp, ans);
        }
    }
};