C++string类常见用法（二）

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同一部分，完全以代码形式作解

#include<string>#include<iostream>using namespace std;int main(){    string str= "hello ";    const char *c = "RALPHFJY ";    str.append(c);    cout<<str<<endl;    const char*ch = "and FUNKYA blablabla";    str.append(ch,10);    cout<<str<<endl;    string str1 = " and ";    string str2 = "forever";    str.append(str1);    str+=str2;    cout<<str<<endl;    string str3 = "@@@!#";    str.append(str3.begin()+3,str3.begin()+4);    cout<<str<<endl;    str.append(7,'h');    cout<<str<<endl;} //append的用法

#include<string>#include<iostream>using namespace std;int main(){    string str1 ="hello";    string str2 = "world";    str1.swap(str2);    cout<<str1<<endl;    cout<<str2<<endl; }

#include <iostream>       // std::cout  #include <string>         // std::string  int main ()  {    std::string str ("There are two needles in this haystack with needles.");    std::string str2 ("needle");    // different member versions of find in the same order as above:    std::size_t found = str.find(str2);    if (found!=std::string::npos)      std::cout << "first 'needle' found at: " << found << '\n';    found=str.find("needles are small",found+1,6);    if (found!=std::string::npos)      std::cout << "second 'needle' found at: " << found << '\n';    found=str.find("haystack");    if (found!=std::string::npos)      std::cout << "'haystack' also found at: " << found << '\n';    found=str.find('.');    if (found!=std::string::npos)      std::cout << "Period found at: " << found << '\n';    // let's replace the first needle:    str.replace(str.find(str2),str2.length(),"preposition");  //replace 用法    std::cout << str << '\n';    return 0;  }

第三处代码来源于网络上的例子

#include<iostream>#include<string>using namespace std;int main(){    string str ="-45";    int signal = stoi(str);    cout<<signal<<endl;    string str2 = "-1.234";    double signal2 = stof(str2);    cout<<signal2+3<<endl;    int num = 123;    string str3 = to_string(num);    cout<<str3[1]<<endl;}

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