c++中string的用法

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

//string的赋值
void f1()
{
string s1 ="shihao";        //string是一个类
string s2 ("bbbbbb");
string s3 = s1;
string s4(10, 'a');     //等价于string s4 ="aaaaaaaaaa";
cout << s1 << endl;
cout << s2 << endl;
cout << s3 << endl;
cout << s4 << endl;
}

//string的遍历
void f2()
{
string s1 = "abcdefg";

//1:数组方式
for(int i = 0;  i < s1.length(); i++)
{
cout << s1[i] << " ";
}
cout << endl;

//2:迭代器
for(string::iterator it = s1.begin(); it != s1.end(); it++)
{
cout << *it << " ";
}
cout << endl;

//3  异常处理
try
{
for(int i = 0; i < s1.length() + 3; i++)
{
cout << s1.at(i) << " ";   //当出现错误时， 会向外抛出异常
}
}
catch(...)
{
cout << "发生异常" << endl;
}

try
{
for(int i = 0;  i < s1.length() + 3; i++)   //出现错误, 不向外抛出异常
{
cout << s1[i] << " ";
}
}
catch(...)
{
cout << "发生异常" << endl;
}
}

//字符指针和sting的转换
void f4()
{
//1:
string s1 = "aaabbb";
cout << s1.c_str() << endl;

//2:
char buf[128] = {0};
s1.copy(buf, 3, 1);    //拷贝3个字符，从1个字符开始(位置下标从0开始)    //注：不会自动加上字符串结束标志
cout << "buf: " << buf << endl;
}

//字符串的连接
void f5()
{
//1:
string s1 = "aaa";
string s2 = "bbb";
s1 = s1 + s2;
cout << "s1: " << s1 << endl;

//2:
string s3 = "333";
string s4 = "444";
s3.append(s4);
cout << "s3: " << s3 << endl;
}

//字符串的查找和替换
void f6()
{
string s1 = "wbm hello wbm 111 wbm 222 wbm 333";

//查找 从查找位置开始第一个出现的下标
int index = s1.find("wbm", 1);  //位置下标从0开始
cout <<"index: " << index << endl << endl;

//查找每一次wbm出现的下标
int offindex = s1.find("wbm", 0);
while (offindex != string::npos)   //不等于-1
{
cout << "offindex: " << offindex << endl;
offindex++;
offindex = s1.find("wbm", offindex);
}

//把所有的wbm换成大写
offindex = s1.find("wbm", 0);
while (offindex != string::npos)   //不等于-1
{
s1.replace(offindex, 3, "WBM");
offindex++;
offindex = s1.find("wbm", offindex);
}
cout << endl << "s1替换后的结果为： " << s1 << endl;

//把aaa替换成大写
string s2 = "aaa bbb ccc";
s2.replace(0, 3, "AAA");    //从第0个位置开始替换3个
cout << endl << "s2: " << s2 << endl;
}

//区间删除和插入
void f7()
{
string s1 = "hello1 hello2 hello1";
string::iterator it = find(s1.begin(), s1.end(), 'l');
if (it != s1.end())
{
s1.erase(it);   //删除
}
cout << "s1删除l以后的结果为：" << s1 << endl;

s1.erase(s1.begin(), s1.end());
cout << "s1全部删除：" << s1 << endl;
cout << "s1的长度为: " << s1.length() << endl;

//插入
string s2 = "BBB";
s2.insert(0, "AAA");
cout << "s2: " << s2 << endl;
}

//大小写转换
void f8()
{
string s1 = "AAAbbb";
transform(s1.begin(), s1.end(), s1.begin(), ::tolower);       //transform(first,last,result,op);
cout << "s1全部转化为小写为: " << s1 << endl;
transform(s1.begin(), s1.end(), s1.begin(), ::toupper);       //transform(first,last,result,op);
cout << "s1全部转化为大写为: " << s1 << endl;
}

int main()
{
f8();
return 0;
}