1. string基本概念

本质:

  • string是C++风格的字符串,而string本质上是一个类

string和char * 区别:

  • char * 是一个指针
  • string是一个类,类内部封装了char*,管理这个字符串,是一个char*型的容器。

特点:
string 类内部封装了很多成员方法,例如:查找find,拷贝copy,删除delete ,替换replace,插入insert
string管理char*所分配的内存,不用担心复制越界和取值越界等,由类内部进行负责

2. string构造函数

#include <iostream>
#include <string>
using namespace std;


void test01()
{
	string s1;  //创建空字符串,调用无参构造函数
	cout << "str1 = " << s1 << endl;
	
	const char* str = "hello world";
	string s2(str);  //把c_string转换成了string
	cout << "str2 = " << s2 << endl;
	
	string s3(s2);  // 调用拷贝构造函数
	cout << "str3 = " << s3 << endl;
	
	string s4(10, 'a');
	cout << "str4 = " << s4 << endl;
}

int main(){
	
	test01();
	
	return 0;
}

3. string赋值操作

#include <iostream>
#include <string>
using namespace std;

// 赋值
void test01()
{
	string str1;   
	str1 = "hello world";  // char*类型字符串赋值给当前的字符串
	cout << "str1 = " << str1 << endl;
	
	string str2;
	str2 = str1;  // 把字符串s赋值给当前的字符串
	cout << "str2 = " << str2 << endl;
	
	string str3;
	str3 = 'a';  // 字符赋值给当前的字符串
	cout << "str3 = " << str3 << endl;
	
	string str4;
	str4.assign("hello c++");  // 把字符串s赋值给当前的字符串
	cout << "str4 = " << str4 << endl;
	
	string str5;
	str5.assign("hello c++", 5);  // 把字符串s的前n个字符赋值给当前的字符串
	cout << "str5 = " << str5 << endl;
	
	string str6;
	str6.assign(str5);  // 把字符串s赋值给当前的字符串
	cout << "str6 = " << str6 << endl;
	
	string str7;
	str7.assign(5, 'x');
	cout << "str7 = " << str7 << endl;
}

int main(){
	test01();
	
	//system("pause");
	
	return 0;
}

4. string字符串拼接

#include <iostream>
#include <string>
using namespace std;


void test01()
{
	string str1 = "我"; 
	str1 += "爱玩游戏";  // 重载+=操作符
	cout << "str1 = " << str1 << endl;
	str1 += ':';   // 重载+=操作符
	cout << "str1 = " << str1 << endl;
	
	string str2 = "LOL DNF"; 
	str1 += str2;   // 重载+=操作符
	cout << "str1 = " << str1 << endl;
	
	string str3 = "I";
	str3.append(" love ");   // 把字符串s连接到当前字符串结尾
	str3.append("game abcde", 4);  // 把字符串s的前n个字符连接到当前字符串结尾
    //str3.append(str2); 
	str3.append(str2, 4, 3); // 从下标4位置开始,截取3个字符,拼接到字符串末尾 
	cout << "str3 = " << str3 << endl;
		
}

int main(){
	
	test01();
	
	//system("pause");

	return 0;
}

5. string查找和替换

#include <iostream>
#include <string>
using namespace std;


// find查找是从左往后,rfind从右往左
// find找到字符串后返回查找的第一个字符位置,找不到返回-1
// replace在替换时,要指定从哪个位置起,多少个字符,替换成什么样的字符串
void test01()
{
	string str1 = "abcdefgde"; 
	int pos = str1.find("de");
	
	if (pos == -1) 
	{ 
		cout << "未找到" << endl; 
	}
	else 
	{ 
		cout << "pos = " << pos << endl; 
	}
	
	pos = str1.rfind("de"); 
	
	cout << "pos = " << pos << endl;
		
}


void test02()
{ 
	//替换 
	string str1 = "abcdefgde"; 
	str1.replace(1, 3, "1111"); 
	cout << "str1 = " << str1 << endl;
}

int main(){
	
	test01();
	test02();
	
	//system("pause");

	return 0;
}

6. string字符串比较

#include <iostream>
#include <string>
using namespace std;


// 字符串比较
void test01()
{
	string s1 = "hello"; 
	string s2 = "aello"; 
	
	int ret = s1.compare(s2); 
	
	if (ret == 0)
	{ 
		cout << "s1 等于 s2" << endl; 
	}
	else if (ret > 0) 
	{ 
		cout << "s1 大于 s2" << endl; 
	}
	else 
	{ 
		cout << "s1 小于 s2" << endl; 
	}		
}


int main(){
	
	test01();

	//system("pause");

	return 0;
}

7. string字符存取

#include <iostream>
#include <string>
using namespace std;


void test01()
{
	string str = "hello world"; 
	for (int i = 0; i < str.size(); i++) 
	{ 
		cout << str[i] << " "; 
	}
	cout << endl; 
	
	for (int i = 0; i < str.size(); i++) 
	{ 
		cout << str.at(i) << " "; 
	}
	cout << endl; 
	
	//字符修改 
	str[0] = 'x';   //通过[]方式取字符
	str.at(1) = 'x';   //通过at方法获取字符
	cout << str << endl;
}


int main(){
	
	test01();

	//system("pause");

	return 0;
}

8. string插入和删除

#include <iostream>
#include <string>
using namespace std;


//字符串插入和删除
void test01()
{
	string str = "hello"; 
	str.insert(1, "111"); 
	cout << str << endl; 
	
	str.erase(1, 3); //从1号位置开始3个字符 
	cout << str << endl;
}


int main(){
	
	test01();

	//system("pause");

	return 0;
}

9. string子串

#include <iostream>
#include <string>
using namespace std;


//子串
void test01()
{
	string str = "abcdefg"; 
	string subStr = str.substr(1, 3); 
	cout << "subStr = " << subStr << endl; 
	
	string email = "hello@sina.com"; 
	int pos = email.find("@"); 
	string username = email.substr(0, pos); 
	cout << "username: " << username << endl;
}


int main(){
	
	test01();

	//system("pause");

	return 0;
}