string相关函数

头文件#include <cctype>

 

输出包含的标点符号

#include <iostream>
#include <string>
#include <cctype>

int main()
{
    std::string s1 = "lolita is a beautiful girl ? yes !";

    //输出其中的标点符号
    for(auto c : s1)
        if(ispunct(c))
            std::cout<<c<<std::endl;
    return 0;
}

将所有小写转换为大写字母

#include <iostream>
#include <string>
#include <cctype>

int main()
{
    std::string s1 = "lolita is a beautiful girl ? yes !";

    for(auto &c : s1)
        if(islower(c))
            c = toupper(c);

    std::cout<<s1<<std::endl;
    return 0;
}

 

将首个单词大写

 

#include <iostream>
#include <string>
#include <cctype>

int main()
{
    std::string s1 = "lolita is a beautiful girl ? yes !";

    for(decltype(s1.size()) index = 0 ;
    index<s1.size()&&!isspace(s1[index]);
    index++)
    {
        s1[index] = toupper(s1[index]);
    }

    std::cout<<s1<<std::endl;
    return 0;
}

 

 

判断首字母大小写

#include <iostream>
#include <string>
#include <cctype>

int main()
{
    std::string s1 = "lolita is a beautiful girl ? yes !";

    if(s1.size()>0) //很重要
    {
        if(isupper(s1[0]))
        {
            std::cout<<"首字母大写"<<std::endl;
        }
        else
        {
            std::cout<<"首字母小写"<<std::endl;
        }
    }
    else
    {
        std::cout<<"空字符串"<<std::endl;
    }

    return 0;
}