【leetcode】Sum Root to Leaf Numbers

/**
* Definition for binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:

int sum;

void dfs(TreeNode *curNode,int tmpSum)
{
if(curNode->left==NULL&&curNode->right==NULL)
{
sum=sum+tmpSum*10+curNode->val;
return ;
}
if(curNode->left!=NULL)
dfs(curNode->left,(tmpSum*10+curNode->val));
if(curNode->right!=NULL)
dfs(curNode->right,(tmpSum*10+curNode->val));
}

int sumNumbers(TreeNode *root) {
// Note: The Solution object is instantiated only once and is reused by each test case.
if(root==NULL)
return 0;

sum=0;
dfs(root,0);
return sum;
}
};