string黑科技

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#include <iostream>

#include <string>

using namespace std;

int main()

{

    string s1;

    s1="i love you";

    string s2(s1);  //把s2初始化为s1的一个副本,注意写法，不能前面先定义s2的类型后面直接写,也不能定义两次s2

    string s3("value");  //将s3初始化一个字符串面值副本

    string s4(10,‘s‘);   //将s4初始化为字符‘s‘的10个副本

    /*注意字符串面值与标准库string不是同一个类型*/

    cout<<s2<<" "<<s3<<" "<<s4<<endl;

    string s5;

    while(cin>>s5)  //这里可以输入“  hello world  ”测试，发现只读取有效字符到遇到空格结束

    {

        cout<<s5<<endl;

    }

    return 0;

}

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#include<iostream>

#include<string>

using namespace std;

int main(){

    string str1;

    string str2("the size of ");

    string str3=" hello world  ";//空格不会忽略

    str3+=str2;

    str3.append("haha secessful");

    cout<<str3<<endl;

    cout<<"the size of is "<<str2.size()<<endl;

    /*注意这里取长度的str2.size()，和str2.length(),但是注意str2.size()返回的值并不是int类型，

    事实表明size_type存储的string长度是int所能存储的两倍*/

    getline(cin,str1);  //read line at time until end-of-file,注意写法。

    while(!str1.empty())  //返回一个bool值，空的话返回true，否则返回false。

    {

        for(string::size_type i=0;i!=str1.size();++i)  //注意size_type类型

        {

            cout<<str1[i];

        }

        cout<<endl;break;

    }

    return 0;

}

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#include <iostream>

#include <string>

#include <cctype>

using namespace std;

int main()

{

    string str1="Hello World!!!";

    string::size_type punct_cnt = 0;

    for(string::size_type i=0;i!=str1.size();++i)

    {

        if(ispunct(str1[i]))

            ++punct_cnt;

        str1[i]=toupper(str1[i]);

    }

    cout<<"字符中标点符号有："<<punct_cnt<<endl;

    cout<<str1<<endl;

    return 0;

}

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#include<iostream>

#include<algorithm>

#include<string>

#include<numeric>

using namespace std;

int main(){

    string s;

    s="54268713";

    reverse(s.begin(),s.end()); //字符串反转

    cout<<s<<endl;

    string s1="i love you";

    string::iterator it;

    it=s1.begin();

    s1.insert(it+1,‘p‘);  //插入

    cout<<s1<<endl;

    string s2("abc123456");

    string::iterator it2=s2.begin();

    s2.erase(it2+6);  //删除

    cout<<s2<<endl;

    s2.erase(it2,it2+3);

    cout<<s2<<endl;

    s2.replace(2,1,"good");  //替换

    cout<<s2<<endl;

    cout<<s2.find("good")<<endl;  //搜索返回下标值

    cout<<s2.compare("12good56")<<endl;  //比较，自行修改值看其返回值

    cout<<s2.compare("12good56758")<<endl;

    return 0;

}

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#include<iostream>

#include<algorithm>

#include<string>

using namespace std;

int main(){

    string s;

    s="123cat&&dog";

    cout<<s.find("cat")<<endl;

    if(s.find("cat")!=string::npos)cout<<"Found"<<endl;

    else cout<<"not Found!"<<endl;

    return 0;

}

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#include<iostream>

#include<string>

using namespace std;

int main(){

    string s="0123456789";

    //cin>>s;

    cout<<s.substr(3,5)<<endl;//34567

    return 0;

}

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#include <iostream>

#include <algorithm>

#include <string>

#include <numeric>

#include <vector>

#include <cstdio>

using namespace std;

int main(int argc,char *argv[])

{

    vector<string> v;   //vector的string

    v.push_back("Iack");

    v.push_back("Mike");

    v.push_back("Tom cluce");

    cout<<v[0]<<endl;

    cout<<v[1][1]<<endl;

    cout<<v[2].size()<<endl;

    char s3[100],s2[100];

    string str3,str2;

    int ab,ac,ad;

    sscanf("abc fsaf","%s %s",s2,s3);  //注意string不能直接用于sscanf

    str3=s3;str2=s2;

    cout<<str3<<" "<<str2<<endl;

    sscanf("4,5$10000","%d,%d$%d",&ab,&ac,&ad);

    cout<<ab<<" "<<ac<<" "<<ad<<endl;

    char s[200];

    cin>>s;

    cin>>s;

    string s1=s;

    printf(s1.c_str());  //c输出字符串对象

    return 0;

}

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#include<cstdio>

#include<iostream>

#include<sstream>

#include<cctype>

#include<string>

#include<cstring>

using namespace std;

int main(){

    double x; string s;

    //string=>double

    s="3.1415";

    istringstream IS(s);  IS>>x;

    printf("%.3f\n",x);

    //double=>string

    x=0.618;

    ostringstream OS;  OS<<x;

    cout<<OS.str()<<endl;  

    return 0;

}