On the submission page, it shows 0ms. Faster then other C++ solutions.

The idea of solution is not new, this is just a simple way to implement it.

```
class Solution {
public:
int result= 0;
int sumNumbers(TreeNode* root) {
if(root) pathSum(root,root->val);
return result;
}
void pathSum(TreeNode * root, int pathResult)
{
if(!root->left && !root->right)
result = result+pathResult;
if(root->left )
{
pathSum(root->left, pathResult*10 + root->left->val);
}
if(root->right)
{
pathSum(root->right, pathResult*10 + root->right->val);
}
}
};
```