leetcode---path-sum-ii---树

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 andsum = 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:    void dfs(int t, vector<int> tmp, vector<vector<int> > &ans, TreeNode *root, int sum)    {        if(!root)            return;        if(!root->left && !root->right)        {            if(t + root->val == sum)            {                tmp.push_back(root->val);                ans.push_back(tmp);                tmp.pop_back();            }        }        tmp.push_back(root->val);        dfs(t+root->val, tmp, ans, root->left, sum);        dfs(t+root->val, tmp, ans, root->right, sum);        tmp.pop_back();    }    vector<vector<int> > pathSum(TreeNode *root, int sum)     {        vector<vector<int> > ans;        vector<int> tmp;        dfs(0, tmp, ans, root, sum);        return ans;    }};