[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.

My Code:

 int sumNumbers(TreeNode *root) {
        if(!root) return 0;
        queue q;
        q.push(root);
        int sum = 0;
        while(!q.empty()){
            TreeNode* cur = q.front();
            if(!cur->left && !cur->right){
                sum = sum + cur->val;
            }
            else{
                if(cur->left){
                    cur->left->val = cur->val*10 + cur->left->val;
                    q.push(cur->left);
                }
                if(cur->right){
                    cur->right->val = cur->val*10 + cur->right->val;
                    q.push(cur->right);
                }
            }
            q.pop();
        }
        return sum;
    }