tring GetDomain(const string& url)//域名
{
	size_t pos = url.find("://");
	if (pos != string::npos)
	{
		size_t sta = pos + 3;
		size_t end = url.find("/", sta);
		if (end != string::npos)
		{
			return url.substr(sta, end - sta);
		}
	}
	else
	{
		return string();//匿名对象
	}
}
string GetProtocol(const string& url)//协议名
{
	size_t pos = url.find("://");
	if (pos != string::npos)
	{
		return url.substr(0, pos - 0);
	}
	else
	{
		return string();//匿名对象
	}

}
int main()
{
	//要求分别取出域名和协议名
	string url1 = "http://www.cplusplus.com/reference/string/";
	string url2 = "https://www.cppreference.com/";
	cout << GetDomain(url1) << endl;
	cout << GetProtocol(url1) << endl;
	cout << GetDomain(url2) << endl;
	cout << GetProtocol(url2) << endl;
	return 0;
}