consecutive_array.cpp

auto consecutive_array(auto input) {
    auto begin = std::begin(input);
    auto end   = std::end(input);

    std::sort(begin, end);
    
    begin = std::begin(input);
    end   = std::end(input);

    decltype(*begin) required;
    
    for (auto itr = begin; itr != end;) {
        auto current = itr;
        auto next    = std::next(itr);

        if (next == end) break;
        
        required += *next - (*current + 1);
        itr = next;
    }
    
    return required;
}

int makeArrayConsecutive2(std::vector<int> statues) {
    return consecutive_array(statues);
}