目录

1.string基本概念

 2.string构造函数,char*

3.string赋值操作

4.string字符串拼接+=,append

5.string查找和替换,find,replace

 6.string字符串比较,compare

7.string字符存取[].at，取，修改单个字符，size返回字符串长度

8.string插入和删除，insert,erase

 9.string截取子串，substr

1.string基本概念

 2.string构造函数,char*

#include<iostream>
using namespace std;

//string构造函数
void test01()
{
	string s1;//默认构造，无参构造，string(),创建一个空字符串

	string s = "abcd";
	cout <<"s= "<< s << endl;

	const char* str = "hello world";
	//C语言风格的字符串初始化c++中的string
	string s2(str);//string(const char *)
	cout << "s2= " << s2 << endl;

	string s3(s2);//拷贝构造，用string对象初始化另一个string对象
	cout << "s3= " << s3 << endl;

	string s4(10, 'a');//用10个a组成一个字符串
	cout << "s4= " << s4 << endl;
}
int main()
{
	test01();




	/*
	char* p = "abcef";//是将字符串a的地址给了p
	
	*p = 'W';
	"abcdf" 字符串是常量，常量不可以更改
	所以报错
	*/
	cout << "__________________________" << endl;
	const char* p = "abcef";
	//常量指针，内容不可更改,指向可以更改
	p = "fg";
	cout << p << endl;
	//为什么不是*p,是将字符串a的地址给了p，然后一直往后读
	//读到\0为止，输出*p会输出a
	system("pause");//按任意键继续
	return 0;
}

3.string赋值操作

#include<iostream>
using namespace std;

//string赋值操作
void test01()
{
	string str1;
	//char*类型字符串 赋值给当前字符串
	str1 = "hello world";//用等号的方法做一个赋值操作
	cout << "str1= " << str1 << endl;

	string str11="zyq";
	//char*类型字符串 赋值给当前字符串
	cout << "str11= " << str11 << endl;

	string str2;
	//把字符串str1赋值给当前的字符串
	str2 = str1;
	cout << "str2= " << str2 << endl;

	string str3;
	//单个字符给字符串赋值，单个字符也可以看成字符串
	str3 = 'a';
	cout << "str3= " << str3 << endl;

	/*
	报错
	string str33='a';
	//单个字符给字符串赋值，单个字符也可以看成字符串
	cout << "str33= " << str33 << endl;
	*/
	

	string str4;
	//char*类型字符串 赋值给当前字符串
	str4.assign("hello C++");
	cout << "str4= " << str4 << endl;

	string str5;
	//把字符串s的前n（包括n）个字符付给当前字符串
	str5.assign("hello C++",5);
	cout << "str5= " << str5 << endl;//输出hello

	string str6;
	//把字符串s付给当前字符
	str6.assign(str5);
	cout << "str6= " << str6 << endl;//输出hello

	string str7;
	//用10个字符w组成的字符串给当前字符串赋值
	str7.assign(10, 'w');
	cout << "str7= " << str7 << endl;
}
int main()
{
	test01();




	
	system("pause");//按任意键继续
	return 0;
}

一般用等号的方式进行赋值。

4.string字符串拼接+=,append

#include<iostream>
using namespace std;

//string字符串拼接

void test01()
{
	string str1 = "我";
	//追加字符串,const char*
	str1 += "爱你";
	cout << "str1= " << str1 << endl;
	//追加字符串 string& str
	string str2 = " love is love";
	str1 += str2;
	cout << "str1= " << str1 << endl;

	//追加字符 const char c
	str1 += '!';
	cout << "str1= " << str1 << endl;

	string str3 = "I";
	//const char* s
	str3.append(" Love");
	cout << "str3= " << str3 << endl;
	//const char* s,的前n个
	str3.append(" You abcd",4);
	cout << "str3= " << str3 << endl;
	//追加字符串 string& str
	str3.append(str2);
	cout << "str3= " << str3 << endl;
	//从pos开始 截取n个字符
	string str4 = "abcdef";
	string str5 = "ghopq";
	str4.append(str5, 2, 3);
	cout << "str4= " << str4 << endl;

}
int main()
{
	test01();

	system("pause");//按任意键继续
	return 0;
}

5.string查找和替换,find,replace

#include<iostream>
using namespace std;

//string字符串查找和替换

//1.查找
void test01()
{
	string str1 = "abcdabc";
	//返回要查找的字符串在str1中第一次出现的位置，查找不到，返回-1
	int pos1 = str1.find("de");
	int pos2 = str1.find("ab");
	cout << "pos1 = " << pos1 << endl;//输出：-1
	cout << "pos2 = " << pos2 << endl;//输出：0

	//rfind
	//rfind从右往左找，计算下标还是从左往右
	//即rfind是输出要查找的字符串在str1中最后一次出现的位置
	int pos3 = str1.rfind("de");
	int pos4 = str1.rfind("ab");
	cout << "pos3 = " << pos3 << endl;//输出：-1
	cout << "pos4 = " << pos4 << endl;//输出：4
}

//2.替换
void test02()
{
	string str1 = "abcdefg";
	//从1号位置起的3个字符替换为字符串"1111"
	str1.replace(1, 3, "1111");
	cout << "str1 = " << str1 << endl;//输出str1 = a1111efg
}
int main()
{
	test01();
	test02();
	system("pause");//按任意键继续
	return 0;
}

 6.string字符串比较,compare

#include<iostream>
using namespace std;

//字符串比较

void test01()
{
	string str1 = "hello";
	string str2 = "xello";
	if (str1.compare(str2) == 0)
	{
		cout << "str1 等于 str2" << endl;
	}
	else if (str1.compare(str2) > 0)
	{
		cout << "str1 大于 str2" << endl;
	}
	else if (str1.compare(str2) < 0)
	{
		//x>h
		cout << "str1 小于 str2" << endl;
	}
}
int main()
{
	test01();
	system("pause");//按任意键继续
	return 0;
}

主要用于判断两个字符串是否相等，判断谁大谁小意义不大。

7.string字符存取[].at，取，修改单个字符，size返回字符串长度

#include<iostream>
using namespace std;

//字符串存取

void test01()
{
	string str = "hello";
	cout << "str = " << str << endl;
	//1.通过[]访问单个字符
	//size返回字符串长度
	for (int i = 0; i < str.size(); i++)
	{
		cout << str[i] << " ";
	}
	cout << endl;
	//2.通过at方式访问单个字符
	for (int i = 0; i < str.size(); i++)
	{
		cout << str.at(i)<< " ";
	}
	cout << endl;

	//修改单个字符
	str[0] = 'x';
	cout << "str = " << str << endl;//输出：xello
	str.at(1) = 'x';
	cout << "str = " << str << endl;//输出：xxllo
}
int main()
{
	test01();
	system("pause");//按任意键继续
	return 0;
}

8.string插入和删除，insert,erase

 9.string截取子串，substr

#include<iostream>
using namespace std;

//string截取子串

void test01()
{
	string str = "abcdef";

	string subStr = str.substr(1, 3);
	cout << "subStr = " << subStr << endl;//subStr = bcd
}
//实用操作
void test02()
{
	string email = "zhangsan@sina.com";
	//从邮件地址中 获取 用户名信息
	int pos= email.find('@');
	string use_name = email.substr(0, pos);
	cout << "use_name = " << use_name << endl;// use_name = zhangsan

}
int main()
{
	test01();
	test02();
	system("pause");//按任意键继续
	return 0;
}