public static OptimalType GetLeastTypeForAllSubcases(int numItems, int groupSize)
{
// This method returns the least type that will be able to handle all subcases without overflowing.
//
// n choose (n / 2) is the worst subcase that generates the most combinations.
// So, if numItems is twice or more groupSize, then there is no subcase that will increase the number of combos.
//
BigInteger numCombos;
OptimalType returnValue;
if (numItems >= groupSize + groupSize)
{
numCombos = Combination.GetNumCombos(numItems, groupSize);
}
else
{
numCombos = Combination.GetNumCombosBigInt(numItems, numItems / 2);
}
// If overflowed ulong, then only big int will work with all subtypes.
if (numCombos > ulong.MaxValue)
{
returnValue = OptimalType.BigInt;
}
else if (numCombos <= uint.MaxValue)
{
returnValue = OptimalType.UnsignedInt;
}
else
{
returnValue = OptimalType.UnsignedLong;
}
return(returnValue);
}
public static OptimalType GetLeastTypeForCase(int numItems, int groupSize)
{
// This method returns the least type that can handle all ranks for the case of numItems choose groupSize.
//
OptimalType returnValue;
BigInteger numCombos = Combination.GetNumCombosBigInt(numItems, groupSize);
// If overflowed ulong, then only big int will work with this case.
if (numCombos > ulong.MaxValue)
{
returnValue = OptimalType.BigInt;
}
else if (numCombos <= uint.MaxValue)
{
returnValue = OptimalType.UnsignedInt;
}
else
{
returnValue = OptimalType.UnsignedLong;
}
return(returnValue);
}