Roman To Integer - Execution Time

final romanNumbers = {
    "I": 1,
    "V": 5,
    "X": 10,
    "L": 50,
    "C": 100,
    "D": 500,
    "M": 1000
  };

void main()
{
    var stopwatch = Stopwatch()..start();
    final int loopCount = 1000000;

    for(var i = 0; i < loopCount; i++) {
        romanToIntShamkhal('MCMXCIV');
    }

    print('Shamkhal\'s Code Executed in ${stopwatch.elapsed}');

    stopwatch = Stopwatch()..start();

    for(var i = 0; i < loopCount; i++) {
        romanToIntKanan('MCMXCIV');
    }

    print('Kanan\'s Code Executed in ${stopwatch.elapsed}');
}


int romanToIntShamkhal(String roman)
{
    return roman.split('')
                .reversed
                .map((n) => romanNumbers[n])
                .reduce((curr, next) => curr > 2 * next ? curr - next : curr + next);
}

int romanToIntKanan(String romanNumber) {
  int calculatedResult = 0;

  for (int i = 0; i < romanNumber.length; i++) {
    var currentCharacter =
        new String.fromCharCode(romanNumber.runes.elementAt(i));

    var nextCharacter;

    if (i < romanNumber.length - 1) {
      nextCharacter =
          new String.fromCharCode(romanNumber.runes.elementAt(i + 1));
    }

    if (nextCharacter != null) {
      calculatedResult += romanNumbers[currentCharacter] *
          (romanNumbers[currentCharacter] >= romanNumbers[nextCharacter]
              ? 1
              : -1);
      continue;
    }

    calculatedResult += romanNumbers[currentCharacter];
  }

  return calculatedResult;
}