C++：string实现查找网址的协议名和后缀

#include <iostream>
using namespace std;

//获取协议名
string GetProtocol(const string& url)
{
	size_t pos = url.find("://");
	if (pos != string::npos)
	{
		return url.substr(0, pos - 0);
	}
	else
	{
		//返回空串
		return string();
	}
}

//获取后缀名
string GetDomain(const string& url)
{
	size_t pos = url.find("://");
	if (pos != string::npos)
	{
		size_t start = pos + 3;         //加三是为了跳过://这三个字符
		size_t end = url.find("/", start);
		if (end != string::npos)
		{
			return url.substr(start, end - start);      //从start开始到end结束
		}
		else
		{
			return string();
		}
	}
}
int main()
{
	string url1 = "https://www.baidu.com/?tn=49055317_13_hao_pg";
	string url2 = "https://www.nowcoder.com/exam/company";
	string url3 = "www.nowcoder.com/exam/company";
	cout << GetDomain(url1) << endl;
	cout << GetDomain(url2) << endl;

	cout << GetProtocol(url1) << endl;
	cout << GetProtocol(url2) << endl;
	cout << GetProtocol(url3) << endl;


	system("pause");
	return 0;
}