frequency_map_wild_desire.cpp

template<typename Value, size_t N>
constexpr std::array<int, N> frequency_map(std::array<Value, N> const& values)
{
  std::map<Value, int> freq_map;
  for (int i = 0; i < N; ++i)
    freq_map[values[i]] += 1;  // Count each occurence using a std::map
    
  std::array<int, N> freqs {}; // Reconstruct a std::array from our std::map
  for (int i = 0; i < N; ++i)
    freqs[i] = freq_map[values[i]];
  return freqs;
}