#include <iostream>
#include <vector>
#include <locale>
#include <sstream>

struct ctype_russian : std::ctype<char>
{
    static const mask* make_table()
    {
        static std::vector<mask> v{classic_table(), classic_table() + table_size};
        for(char c: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ") {
            v[(unsigned char)c] &= ~alpha;
            v[(unsigned char)c] |=  space;
        }
        for(char c: "абвгдеёжзийклмнопрстуфхцчшщъыьэюяАБВГДЕЁЖЗИЙКЛМНОПРСТУФХЦЧШЩЪЫЬЭЮЯ") {
            v[(unsigned char)c] |=  alpha;
            v[(unsigned char)c] &= ~space;
        }
        return &v[0];
    }
    ctype_russian(std::size_t refs = 0) : ctype(make_table(), false, refs) {}
};

int main()
{
    std::string in = "English words Русские слова English again";
    std::istringstream s(in);
    s.imbue(std::locale(s.getloc(), new ctype_russian()));
    std::string token;
    while (s >> token)
        std::cout << "  " << token << '\n';
}