void get_height(TreeNode *cur, height &h) {
	if (!cur) {
		h = 0;
		return;
	}
	int left_height, right_height;
	left_height = right_height = 0;
	get_height(cur->left, h);
	left_height = h;
	get_height(cur->right, h);
	right_height = h;
	h = 1 + std::max(left_height, right_height);
}