digital clock luminozity

num oneSectionLumen = 1.0;
num doublePointLumen = .45;

List<int> sectionForDigits = [6,2,5,5,4,5,6,3,7,6];
Map<String, num> lumensPerChar = {};
Map<String, num> lumensForHour = {};

void main() {
  for(int i = 0 ; i < 10; i++) {
    lumensPerChar["$i"] = sectionForDigits[i] * oneSectionLumen;
  }
  lumensPerChar[':'] = doublePointLumen;
  String x = "${lumensPerChar[lumensPerChar.keys.first]}";

  num lumenChange = 0;
  List<String> hourConcerned = [];

  String prevKey = '';
  num prevLumen = null;
  for(int h = 0; h < 24; h++) {
    String hour = h < 10 ? "0$h":"$h";
    for(int m = 0; m < 60; m++) {
        String minutes = m < 10 ? "0$m":"$m";

      String key = "$hour:$minutes";
      num lumen = _calculLumenFor(key);
      //print("'$key' : $lumen,");

      if(prevLumen != null) {
        num absChange = (prevLumen - lumen).abs();
        if(absChange > lumenChange) {
          lumenChange = absChange;
          hourConcerned = ['$prevKey to $key'];
        } else if(absChange == lumenChange) {
          hourConcerned.add('$prevKey to $key');
        }
      }
      prevKey = key;
      prevLumen = lumen;

      lumensForHour[key] = lumen;
    }
  }

  print(hourConcerned);
  print(lumenChange);
//   for(String s in lumensForHour.keys) {
//     print("$s, ");
//   }
//   print("---------------------------");
//   for(num n  in lumensForHour.values) {
//     print("$n, ");
//   }

}

num _calculLumenFor(String str) {
  num lumen = 0;
  for(String char in str) {
    lumen += lumensPerChar[char];
  }
  return lumen;
}