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.

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


   void sumRootToLeaf(TreeNode *root, int num, int *res)  
   {  
     if(!root)return;  
     if(!root->left && !root->right )  
     {  
       *res += num *10 + root->val;  
       return;  
     }  
     sumRootToLeaf(root->left, 10*num+root->val,res);  
     sumRootToLeaf(root->right, 10*num+root->val,res);  
   }  
   int sumNumbers(TreeNode *root) {  
      int res = 0;  
      sumRootToLeaf(root,0,&res);  
      return res;  
   }