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