#include <string>
#include <iostream>
#include <algorithm>
#include <iterator>
int main()
{
std::string s1 = "11111211";
std::cout << "before: " << s1 << '\n';
std::string s2;
std::unique_copy(s1.begin(), s1.end(), std::back_inserter(s2));
std::cout << "after: " << s2 << '\n';
}