customSortNumbers.cpp

std::vector<int> customSortNumbers(std::vector<int> arr) {
    // arr[0] = 1
    // count[1] = 1
    // count[arr[i]] 
    // map
    /*
    {1, 1}
    {2, 3}
    {4, 2}
    */
    std::map<int, int> occurrences;
    // {{1, 1},{4, 2},{2, 3}}
 
    std::pair<int,int> temp_occurrence;
    for (int i = 0; i < arr.size(); ++i) {
        //printf("occurrences: %d %d\n", arr[i], occurrences[arr[i]]);
        if (occurrences.find(arr[i]) != occurrences.end()) {             
            occurrences[arr[i]] += 1;
        } else {
            temp_occurrence = {arr[i], 1};
            occurrences.insert(temp_occurrence);
        }
    }

    std::set<std::pair<int,int>> output_set;
    
    auto it = occurrences.begin();
    std::pair<int, int> temp;
    while (it != occurrences.end()) {
        temp = *it;
        output_set.insert({temp.second, temp.first});
        //printf("%d %d\n", temp.first, temp.second);
        ++it;
    }

    auto set_it = output_set.begin();
    std::vector<int> output;
    while (set_it != output_set.end()) {
        temp = *set_it;
        for (int k = 0; k < temp.first; ++k) {
            output.push_back(temp.second);
        }
        ++set_it;
    }
    return output;
}