LeetCode - Sum Root to Leaf Numbers

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path 1->2->3 which represents the number 123.

Find the total sum of all root-to-leaf numbers.

For example,

    1
   / \
  2   3

The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.

int sumFun(TreeNode* root, int sum) {
    if (NULL == root) {
        return 0;
    }

    sum = sum * 10 + root->val;

    if ((root->left == NULL) && (root->right == NULL))
    {
        return sum;
    }

    int l = sumFun(root->left, sum);
    int r = sumFun(root->right, sum);

    return l + r;
}

int sumNumbers(TreeNode *root) {
    // Start typing your C/C++ solution below
    // DO NOT write int main() function
    return sumFun(root, 0);
}