Leetcode #113 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]
]

Difficulty:Medium

/**
* 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<vector<int> > ans;
void path(TreeNode* root, int sum,vector<int>& nums){
if(root==NULL)
return;
nums.push_back(root->val);
vector<int> nums2 = nums;
if(sum-root->val==0&&root->left==NULL&&root->right==NULL)
{
ans.push_back(nums);
}
path(root->left,sum-root->val,nums);
path(root->right,sum-root->val,nums2);
}
vector<vector<int> > pathSum(TreeNode* root, int sum) {
vector<int> nums;
path(root,sum,nums);
return ans;

}
};