【leetcode】129. 求根到叶子节点数字之和

int sum(struct TreeNode* root, int tmp_sum) 
{
    if (root == NULL) return 0;
    if (root->left == root->right) {
        return tmp_sum * 10 + root->val;
    }
    return sum(root->left,  tmp_sum * 10 + root->val) + 
           sum(root->right, tmp_sum * 10 + root->val);
}
int sumNumbers(struct TreeNode* root){
    return sum(root, 0);
}

int sum(struct TreeNode* root, int tmp_sum) 
{
    if (root == NULL) return 0;
    if (root->left == root->right) {
        return tmp_sum * 10 + root->val;
    }
    return sum(root->left,  tmp_sum * 10 + root->val) + 
           sum(root->right, tmp_sum * 10 + root->val);
}
int sumNumbers(struct TreeNode* root){
    return sum(root, 0);
}