/// <summary>
/// Can a meld be added to the current accumulator?
/// </summary>
private bool CanAddMeld(int index, Mentsu mentsu)
{
if (index > TypesInSuit - mentsu.Stride)
{
return false;
}
var max = TilesPerType - mentsu.Amount;
return Accumulator.Skip(index).Take(mentsu.Stride).All(i => i <= max);
}
/// <summary>
/// Creates all possible combinations of used tiles for a number of melds in a single suit by adding a specific meld.
/// </summary>
private IEnumerable<Combination> Create(int remainingMelds, int currentIndex, Mentsu mentsu)
{
var indices = Enumerable.Range(currentIndex, TypesInSuit - currentIndex);
var freeIndices = indices.Where(i => CanAddMeld(i, mentsu));
foreach (var index in freeIndices)
{
AddToAccumulator(index, mentsu.Stride, mentsu.Amount);
foreach (var combination in Create(remainingMelds - 1, index))
{
yield return combination;
}
AddToAccumulator(index, mentsu.Stride, -mentsu.Amount);
}
}