sum-root-to-leaf-numbers leetcode C++

Given a binary tree containing digits from0-9only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path1->2->3which represents the number123.

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

For example,

1

/ 
2 3

The root-to-leaf path1->2represents the number12. The root-to-leaf path1->3represents the number13.

Return the sum = 12 + 13 =25.

C++

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int sumNumbers(TreeNode *root){
        if(NULL == root) return 0;
        int sum = 0;
        sum  = getSum(root,0);
        //getSum2(root,0,sum);
        return sum;
    }
    void getSum2(TreeNode *root, int num, int &sum){
        num = num * 10 + root->val;
        if(NULL == root->left && NULL == root->right){
            sum += num;
            return;
        }
        if(root->left)
            getSum2(root->left, num, sum);
        if(root->right)
            getSum2(root->right, num, sum);
    }
    int getSum(TreeNode* root, int num){
        num = num * 10 + root->val;
        if(NULL == root->left && NULL == root->right)
            return num;
        int sum = 0;
        if (NULL != root->left) sum += getSum(root->left,num);
        if (NULL != root->right) sum += getSum(root->right,num);
        return sum;
    }
};