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 {
private:
    int mysum;
    vector<vector<int>> v;
    int time;
public:
    void tra(TreeNode* root,int sum,vector<int> res)
    {
        if(root==NULL){
            return;
        }
        res.push_back(root->val);
        sum+=root->val;
        if(sum==mysum&&root->left==NULL&&root->right==NULL){
            v.push_back(res);
            return;
        }
        tra(root->left,sum,res);
        tra(root->right,sum,res);
    }

    vector<vector<int>> pathSum(TreeNode *root, int sum) {
        time=0;
        mysum=sum;
        vector<int> res;
        tra(root,0,res);
        return v;
    }
};