Sum Root to Leaf Numbers

/*

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) {}
 * };
 */
class Solution {
public:
    void getSum(TreeNode *curr, int pathSum, int & sum){
       if(curr == NULL){
          return;
       }
       pathSum = pathSum*10 + curr->val;
       if(curr->left==NULL && curr->right==NULL) sum = sum + pathSum;
       getSum(curr->left, pathSum, sum);
       getSum(curr->right, pathSum, sum);
    }
   
    int sumNumbers(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int pathSum = 0;
        int sum = 0;
        getSum(root,pathSum,sum);
        return sum;
    }
};