randIntExcluding function

int randIntExcluding(int min, int max, int exclude)

This method generates and returns a random integer from min to max (inclusive), excluding exclude.

If min, max, and exclude are all the same number, an exception is thrown.

Implementation

int randIntExcluding(int min, int max, int exclude) {
  // If `min`, `max`, and `exclude` are all the same number, throw an
  // exception.
  if (min == max && max == exclude) {
    throw Exception('min, max, and exclude cannot all be the same number.');
  }

  // If `min` and `max` are the same number, just return that number.
  if (min == max) {
    return min;
  }

  // If `min` is greater than `max`, swap their values.
  if (min > max) {
    final int temp = min;
    min = max;
    max = temp;
  }

  // If `exclude` is less than `min` or greater than `max`, just return a
  // random number in the range.
  if (exclude < min || exclude > max) {
    return randInt(min, max);
  }

  // If `exclude` is equal to `min` or `max`, return a random number in the
  // range, excluding `exclude`.
  if (exclude == min) {
    return randInt(min + 1, max);
  } else if (exclude == max) {
    return randInt(min, max - 1);
  }

  // Random numbers on both sides of `exclude`.
  List<int> randNums = [];

  // Generate a random number in the range, excluding `exclude`.
  randNums.add(randInt(min, exclude - 1));
  randNums.add(randInt(exclude + 1, max));

  return randNums[randInt(0, 1)];
}