LeetCode112. Path Sum

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.
For example:Given the below binary tree and sum = 22
,5 / \ 4 8 / / \ 11 13 4 / \ \ 7 2 1
return true, as there exist a root-to-leaf path 5->4->11->2
which sum is 22.

class Solution {
public:
    vector<int> v;
    void dfs(TreeNode* root,int temp){
        if(root->left==NULL&&root->right==NULL){ 
            v.push_back(temp);
            return;
        }
        if(root->left){
            dfs(root->left,temp+root->left->val);
        }
        if(root->right){
            dfs(root->right,temp+root->right->val);
        }
    }
    bool hasPathSum(TreeNode* root, int sum) {
        int res=0;
        bool is=false;
        if(root==NULL) return false;
        dfs(root,root->val);
        for(int i=0;i<v.size();i++){
            if(v[i]==sum){
                is=true;
            }
        }
        return is;
    }
};