[C++知识库]C++字符串string的读取、增删、查找、比较、截取子串、判断一个字符串中包含另一个字符串

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<string>

using namespace std;

void test1()//比较两个字符串
{
	string s1;
	s1.assign("abcdefg");//初始化，赋值
	string s2 = "vbcdefg";//初始化，赋值
	if (s1.compare(s2) == 0)//比较大小
	{
		cout << "S1等于S2" << endl;
	}
	else if (s1.compare(s2) > 0)
	{
		cout << "S1大于S2" << endl;
	}
	else
		cout << "S1小于S2" << endl;
	s1.append(s2);
	cout << "拼接后的S1为：" <<s1<< endl;
}
void test2()//查找并将字符串中字符替换
{
	string s1;
	s1.assign("abcdefgde");//初始化
	int p = s1.find("de");//查找de首次出现的位置，并返回下标，find（）是从前往后找，rfind（）是从后往前找
	cout << "替换前S1为：" << s1 << endl;
	cout << "test2字符串de出现的位置为：" << p << endl;
	s1.replace(1, 3, "1111");//从第1个字符开始，将其及之后共三个字符替换为1111
	cout << "替换后S1为：" << s1 << endl;
	
}

void test3()//读取字符串中的字符
{
	string s1 = "hello";
	for (unsigned int i = 0; i < s1.size(); i++)
	{
		cout <<" " <<s1[i];
	}
	cout << endl;
	for (unsigned int i = 0; i < s1.size(); i++)
	{
		cout << " " << s1.at(i);
	}
	cout << endl;
	s1[0] = 'c';
	cout << s1 << endl;
	cout << endl;
	s1.at(1) = 'c';
	cout << s1 << endl;
}
void test4()//插入和删除
{
	string s1 = "hello";
	s1.insert(0,"222");//插入
	cout << s1 << endl;
	s1.erase(0, 4);
	cout << s1 << endl;
}
void test5()
{
	string s1 = "zhangsan@china.com";
	string s2 = s1.substr(0, 4);
	cout << s2 << endl;
	int r = s1.find("@");
	s2 = s1.substr(0, r);//获取邮件箱中的用户名
	cout << s2 << endl;
}
bool test6()//判断S2字符串是否是S1字符串的字串
{
	string s1 = "hello";
	string s2 = "el";
	if (s1.find(s2) !=-1)//查找不到find()返回-1，查找到则返回下标值
	{
		return true;//是子串
	}
	else
		return false;//不是字串
}
int main()
{
	//test1();//比较两个字符串
	//test2();//查找并将字符串中字符替换
	//test3(); //读取字符串中的字符
	//test4();//字符串的插入和删除
	//test5();//截取字符串当中的子串
	bool i=test6();
	if (i == true)
	{
		cout << "S2是S1的子串" << endl;
	}
	else
		cout << "S2不是S1的子串" << endl;
	return 0;
}