string的增删改查

赋值操作：=，assign()

追加，插入：append(), push_back(), insert()

大小：size(), length(), capacity()

位置访问：[ ], at()

擦除字符：erase()

替换：replace()

比较：compare()

交换：swap()

子串：substr()

判断是否为空：empty()

删除全部字符：clear()

以C string形式返回：c_str()

以字符数组形式返回: data()

查找字符或字符串：find(), find_first_of(), find_last_of(),

反向查找：rfind()

代码一：

#include "stdafx.h"
#include "iostream"
#include <string>
using namespace std;
int main()
{
	string s;	// 默认构造函数，s为空串
	s.assign("my book");//等同于=，将"my book"赋值给s
	cout<<"s.assign()="<<s<<endl;
	// push_back 追加单个字符
	s.push_back('AB');
	cout<<"s.push_back()="<<s<<endl;
	s.append("!!");	//追加,字符串之后追加
	cout<<"s.append()="<<s<<endl;
	// 字符串现有的字符数，size()和length()等效
	cout<<"The size of s "<<s<<" is "<<s.size()<<endl; //int size()
	cout<<"The length of s "<<s<<" is "<<s.length()<<endl; //int length()
	cout<<"The capacity of s "<<s<<" is "<<s.capacity()<<endl; //int capacity() 
	// max_size() 当前C++字符串最多能包含的字符数
	cout<<"The max size of s "<<s<<" is "<<s.max_size()<<endl; //int max_size()
	// 下表操作符[]和at()对所在位置的字符进行访问，at()会检查索引是否有效（0-length()）
	cout<<"s.at(3)="<<s.at(3)<<endl;
	cout<<"s[3]="<<s[3]<<endl;
	cout<<"s="<<s<<endl;
	cout<<"string s after erase(5) is "<<s.erase(5)<<endl; //从索引5开始往后全删除
	s.assign("The cup is very beautiful!");
	cout<<"s="<<s<<endl;	
	cout<<"string s replace(2,3,\"good\") is "<<s.replace(2,3,"good")<<endl;//从索引2开始的3个替换为“good”
	cout<<"string s after erase(7，5) is "<<s.erase(7,5)<<endl; //从索引7开始往后删5个
	s.insert(3,"lovely"); //在位置3处插入逗号后的字符串
	cout<<"s.insert()="<<s<<endl;	
	system("pause");
	return 0;
}

输出结果：

代码二：

#include "stdafx.h"
#include "iostream"
#include <string>
using namespace std;
int main()
{             
	string str="my book!";
	string::size_type pos;
	pos=str.find("book"); // find函数返回字符串“book”在str中第一次出现的位置（下标）
	if(pos!=str.npos) // 如果没找到“book”，返回npos，一个很大的值
	{
		cout<<"book 出现的下标是："<<pos<<endl;
	}
	str.assign("welcome to china.");
	pos=str.find("to",6); // 从str下标6‘e’开始，查找字符串“to”，返回to在str中的下标
	cout<<"str.find(to,6) is :"<<pos<<endl;
	pos=str.rfind("to");// 反向查找
	cout<<"str.rfind(to) is :"<<pos<<endl;
	string substr="o"; // 定义字串为"o"
	cout<<"str.find_first_of(substr):"<<str.find_first_of(substr)<<endl;
	cout<<"str.find_last_of(substr):"<<str.find_last_of(substr)<<endl;
	system("pause");
	return 0;
}

输出结果：

代码3：

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

int main()
{
	string str1; //默认构造函数，创建一个长度为0的字符串
	string str2("hello"); //直接初始化 "hello"
	string str3 = "world"; //赋值初始化 "world"
	string str4(str2); //拷贝构造函数 "hello"
	string str5(str3,1,4); //从字符串str3的位置1（第2个字符）开始取4个字符，用来初始化str5 "orld"
	string str6(str2,2); //用指针str3指向的字符串中的第2个字符开始初始化string对象str6  “llo”
	string str7(8,'s'); //用8个重复的字符's'来初始化string类的对象str7  "ssssssss"

	cout<<"str1 = "<<str1<<endl;
	cout<<"str2 = "<<str2<<endl; //"hello"
	cout<<"str3 = "<<str3<<endl; //"world"
	cout<<"str4 = "<<str4<<endl; //"hello"
	cout<<"str5 = "<<str5<<endl; //"orld"
	cout<<"str6 = "<<str6<<endl; //“llo”
	cout<<"str7 = "<<str7<<endl; //"ssssssss"
	cout<<endl;

	str1.append("my cup");//将字符串"my cup"追加到字符串str1之后
	str2.assign("good luck");//将“good luck”赋值给str2
	cout<<"str11 = "<<str1<<endl; //"my cup"
	cout<<"str21 = "<<str2<<endl; //“good luck”
	str1.insert(3,"green "); //将“green”插入到str1的第3个位置（下标）
	cout<<"str12 = "<<str1<<endl; //"my green cup"
	string str22 = str2.substr(0,4);//从字符串str2的第0个位置取4个字符 "good"
	cout<<"str22 = "<<str22<<endl;
	int pos = str1.find("cup"); //在字符串str1中查找“cup”并返回第一次出现的位置
	cout<<"pos = "<<pos<<endl;
	str3.swap(str7); //交换str3和str7的内容
	if(str1.compare(str2)==0)
	{
		cout<<"str1 is equal to str2."<<endl;
	}
	else if(str1.compare(str2)>0)
	{
		cout<<"str1 is bigger than str2."<<endl;
	}
	str2+=str1;
	cout<<"str23 = "<<str2<<endl;
	system("pause");
	return 0;
}

输出结果：