对称二叉树

1 bool compare(Node* left, Node* right) {
2     if (left == NULL && right != NULL) return false;
3     else if (left != NULL && right == NULL) return false;
4     else if (left == NULL && right == NULL) return true;
5     // 排除了空节点，再排除数值不相同的情况
6     else if (left->data_ != right->data_) return false;
7     return compare(left->left, right->right)&& compare(left->right, right->left);
8 }