Implementation of mergesort in dart

mergesort.dart

void main() {
  final l1 = [1,3,5,9,11, 23,201,202];
  final l2 = [2,2,3,9,10,300,301,415,500];
  final a = new List<int>(l1.length + l2.length);
  _merge(l1, l2, a);
  print(a);

  final sorted = [99,54,10534,42,9,2,4,4,23,54,62,88,33,101,1,2,2,1,7,4,77,6,143];
  mergeSort(sorted);
  print(sorted);
}

void _merge(List<int> left, List<int> right, List<int> a){
  assert(a.length == left.length + right.length);
  final leftBound = left.length;
  final rightBound = right.length;
  final total = leftBound + rightBound;
  int i = 0;
  int curL = 0;
  int curR = 0;

  while(curL + curR < total){
    if(curL >= leftBound){
      for(int j = curR; j < rightBound; j++){
        a[i++] = right[curR++];
      }
    } else if (curR >= rightBound){
      for(int j = curL; j < leftBound; j++){
        a[i++] = left[curL++];
      }
    }else{
      if(left[curL] < right[curR]){
        a[i++] = left[curL++];
      } else {
        a[i++] = right[curR++];
      }
    }
  }

  if(total == 2){
    if(a[0] > a[1]){
      final tmp = a[0];
      a[0] = a[1];
      a[1] = tmp;
    }
  }
}

void mergeSort(List<int> array){
  final arrayBound = array.length;

  if(arrayBound < 2) {
    return;
  }

  final isOdd = arrayBound % 2 == 1;
  final half = (arrayBound / 2).floor();
  final left = new List(half);
  final rBound = half + (isOdd ? 1 : 0);
  final right = new List(rBound);
  for(int i = 0; i < half; i++){
    left[i] = array[i];
    right[i] = array[i + half];
  }

  if(isOdd){
    right[rBound - 1] = array[arrayBound - 1];
  }

  mergeSort(left);
  mergeSort(right);
  _merge(left, right, array);
}