[C++提高编程]（三）：STL-string容器

string基本概念

本质

• string是c++风格的字符串，本质上是一个类

string和char *的区别

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

特点

• string类内部封装了很多成员函数
• 查找find、拷贝copy、删除delete、替换replace、插入insert
• string管理char*分配的内存，不用担心越界等问题，由类内部进行负责

string构造函数

• string();                                 //默认构造，创建一个空字符串
• string(const char* s);            //使用字符串s初始化
• string(const string& str);       //使用一个string对象初始化另一个string对象
• string(int n, char c);              //使用n个字符c初始化

#include <iostream>
#include <string>

using namespace std;


void test(void)
{
	string s1;//默认构造，创建一个空字符串

	const char* str = "Hello World!";
	string s2(str);//使用字符串s初始化

	cout << "s2=" << s2 << endl;

	string s3(s2);//使用一个string对象初始化另一个string对象
	cout << "s3=" << s3 << endl;

	string s4(10, 'a'); //使用n个字符c初始化
	cout << "s4=" << s4 << endl;
}


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

string赋值操作

#include <iostream>
#include <string>

using namespace std;

void test(void)
{
	string str1;

	str1 = "Hello World.";
	cout << "str1 =" << str1 << endl;

	string str2 = str1;
	cout << "str2 =" << str2 << endl;

	string str3;
	str3 = 'a';
	cout << "str3 =" << str3 << endl;

	string str4;
	str4.assign("Hello C++!");
	cout << "str4 =" << str4 << endl;

	string str5;
	str5.assign("Hello C++!", 5);
	cout << "str5 =" << str5 << endl;

	string str6;
	str6.assign(str5);
	cout << "str6 =" << str6 << endl;
	
	string str7;
	str7.assign(5, 'a');
	cout << "str7 =" << str7 << endl;
}

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

string字符串拼接

#include <iostream>
#include <string>

using namespace std;

void test(void)
{
	string str1 ="我";

	str1 += "爱玩游戏";
	cout << "str1 = " << str1 << endl;

	str1 += ':';
	cout << "str1 = " << str1 << endl;

	string str2("LOL/DNF");
	str1 += str2;
	cout << "str1 = " << str1 << endl;

	string str3 = "I";
	str3.append(" Love ");
	cout << "str3 = " << str3 << endl;

	str3.append("game abcde", 4);
	cout << "str3 = " << str3 << endl;

	str3.append(":LOL ");
	cout << "str3 = " << str3 << endl;

	str3.append("DNF GG", 0, 3);
	cout << "str3 = " << str3 << endl;
}

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

string查找和替换

#include <iostream>
#include <string>

using namespace std;

void test(void)
{
	string str1 ="abcdefde";

	int pos = str1.find("de");

	if (pos == -1)
	{
		cout << "未找到字符串" << endl;
	}
	else {
		cout << "找到字符串：" << pos << endl;
	}
	//rfind从右往左查找，find从左往右查找
	pos = str1.rfind("de");
	if (pos == -1)
	{
		cout << "未找到字符串" << endl;
	}
	else {
		cout << "找到字符串：" << pos << endl;
	}

	string str2 = "hello";
	cout << "str1替换前:" << str1 << endl;
	//从0个字符起3个字符替换为str2
	str1.replace(0, 3, str2);
	cout << "str1替换后:" << str1 << endl;

}

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

string字符串比较

比较方式：按字符的ASCII码进行对比

• = 返回 0
• > 返回 1
• < 返回 -1

string字符串存取

#include <iostream>
#include <string>

using namespace std;

void test(void)
{
	string str1 ="abcdefde";

	cout << str1[0] << endl;
	str1[0] = 'x';
	cout << str1[0] << endl;

	cout << str1.at(1) << endl;
	str1.at(1) = 'm';
	cout << str1[1] << endl;
	cout << str1 << endl;
}

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

string字符串插入和删除

#include <iostream>
#include <string>

using namespace std;

void test(void)
{
	string str1 ="abcdefde";
	cout << "str1 = " << str1 << endl;

	str1.insert(1, "Hello");
	cout << "str1 = " << str1 << endl;

	str1.erase(1, 5);
	cout << "str1 = " << str1 << endl;
}

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

string字串

#include <iostream>
#include <string>

using namespace std;

void test(void)
{
	string str1 ="san.Liu@qq.com";
	cout << "str1 = " << str1 << endl;
	
	int pos = str1.find('@');
	cout << "pos = " << pos << endl;

	string Substr = str1.substr(0, pos);
	cout << "str1 = " << Substr << endl;
}

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

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