Question

IF a string may include several un-necessary elements, e.g., such as @, #, $,%.

How to find them and delete them?

I know this requires a loop iteration, but I do not know how to represent sth such as @, #, $,%.

If you can give me a code example, then I will be really appreciated.

Answer 1

The usual standard C++ approach would be the erase/remove idiom:

#include <string>
#include <algorithm>
#include <iostream>
struct OneOf {
        std::string chars;
        OneOf(const std::string& s) : chars(s) {}
        bool operator()(char c) const {
                return chars.find_first_of(c) != std::string::npos;
        }
};
int main()
{
    std::string s = "string with @, #, $, %";
    s.erase(remove_if(s.begin(), s.end(), OneOf("@#$%")), s.end());
    std::cout << s << '\n';
}

and yes, boost offers some neat ways to write it shorter, for example using boost::erase_all_regex

#include <string>
#include <iostream>
#include <boost/algorithm/string/regex.hpp>
int main()
{
    std::string s = "string with @, #, $, %";
    erase_all_regex(s, boost::regex("[@#$%]"));
    std::cout << s << '\n';
}