Untitled

#include <iostream>
#include <set>
#include <sstream>
#include <string>
std::string solution(std::string& S)
{

    std::istringstream    ist(S);
    std::string           tmp;
    std::set<std::string> music_set{ ".mp3", ".vaw" },
        img_set{ ".jpg", ".png" }, mov_set{ ".mp4", ".avi" };
    int  count = 1, music = 0, img = 0, mov = 0, etc = 0;
    int* it;

    while (ist >> tmp)
    {
        if (count % 2)
        {
            std::string format_fille = tmp.substr(
                tmp.find_last_of('.', tmp.size() - 1), tmp.size() - 1);
            if (music_set.find(format_fille) != music_set.end())
            {
                it = &music;
            }
            else if (img_set.find(format_fille) != img_set.end())
            {
                it = &img;
            }
            else if (mov_set.find(format_fille) != mov_set.end())
            {
                it = &mov;
            }
            else
            {
                it = &etc;
            }
        }
        else
        {
            tmp.pop_back();
            int N = stoi(tmp);
            *it += N;
        }
        ++count;
    }
    std::string result;
    result = "music " + std::to_string(music) + "b\n" + "img " +
             std::to_string(img) + "b\n" + "mov " + std::to_string(mov) +
             "b\n" + "etc " + std::to_string(etc) + "b\n";
    return result;
}