#include <ctype.h>
#include <iostream>
#include <algorithm>

using namespace std;

int main()
{
string s = "привет";
transform(s.begin(), s.end(), s.begin(), (int(*)(int)) toupper);
cout << s << endl;
}

#include <ctype.h>
#include <iostream>
#include <algorithm>

using namespace std;

int main()
{
string s = "привет";
locale loc("ru_RU.utf8");
const ctype<char>& ct = use_facet<ctype<char> >(loc);
transform(s.begin(), s.end(), s.begin(), std::bind1st(std::mem_fun(&ctype<char>::toupper), &ct));
cout << s << endl;
}