C++ Primer第四版习题--3.10

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

int main()
{
    std::string str, result_str;
    bool flag=false;
    while(getline(std::cin, str))
    {
        for(unsigned index=0; index<str.size(); ++index)
        {
            char ch;
            ch = str[index];
            if(ispunct(ch))
                flag = true;
            else
                result_str += ch;
        }
        if(flag)
            std::cout << result_str << std::endl;
        else
            std::cout << "no flag" << std::endl;
    }
    return 0;
}