判断二叉树是否为满二叉树

struct node {
	int val;
	node *left, *right;
};

int height(node *root) {
	if (!root) return 0;
	int left  = height(root->left);
	int right = height(root->right);
	return max(left, right) + 1; 
}


void count(node *root, int &sum) {
	if (root) {
		sum += 1;
		count(root->left);
		count(root->right);
	}
}

bool isFBT(node *root) {
	if (!root) return 1;
	int sum = 0;
	int h = height(root);
	count(root, sum);
	return sum == pow(2, h) - 1;
}