#include <algorithm>
#include <cstddef>
#include <string>
#include <iostream>
#include <map>

size_t duplicateCount(const std::string& in); // helper for tests

std::string toLower(const char* input){
    std::string temp = input;
    std::transform(temp.begin(), temp.end(), temp.begin(), ::tolower);
    return temp;
}

size_t duplicateCount(const char* in)
{
    // Convert to lower chars
    std::string input = toLower(in);

    // Start counting for every char
    std::map<char, int> my_map;
    for(auto character: input){
        auto it = my_map.find(character);
        if(it != my_map.end()){
            it->second += 1;
        } else {
            my_map[character] = 1;
        }
    }

    // Count how often we have a value higher than 1
    int count = 0;
    for(auto it: my_map){
        if(it.second > 1)
            count++;
    }
    return count;
}

int main(){
    std::cout << duplicateCount("TESTtest");
}