static long distinctCount(IEnumerable <long> source, long length, long remaining, long skippable)
{
if (skippable < 0L)
{
return(0L);
}
if (skippable == 0L)
{
return(Combinatoric.Multinomial(source));
}
var count = source.First();
if (count >= length)
{
return(remaining.Power((int)length));
}
var others = source.Skip(1);
var result = distinctCount(others, length, remaining - 1L, skippable - count);
for (var x = 1L; x <= count; x++)
{
var temp = distinctCount(others, length - x, remaining - 1L, skippable + x - count);
result = checked (result + Combinatoric.Choose(length, x) * temp);
}
return(result);
}
public static void Multinomial()
{
//this example shows how to get multinomial
//use Combinatoric.Multinomial(collection_of_x) to get multinomial
Console.WriteLine(Combinatoric.Multinomial(new[] { 1, 4, 4, 2 }));
}
