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]
]

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/**
* 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:
void findPath(vector<vector<int>> &res, vector<int> vec, TreeNode *root, int remain) {
if(root!=NULL && root->left==NULL && root->right==NULL) {
if(remain == root->val) {
vec.push_back(root->val);
res.push_back(vec);
}
return;
}

if(root==NULL) return ;
//if(root!=NULL && root->val > remain) return;
vec.push_back(root->val);
findPath(res, vec, root->left, remain-root->val);
findPath(res, vec, root->right, remain-root->val);

return;
}
vector<vector<int>> pathSum(TreeNode *root, int sum) {
vector<vector<int>> res;
vector<int> vec;

findPath(res, vec, root, sum);

return res;
}
};