// NOTE: Trully random calculation would involve picking a random combination of change from every single
// possible combination of denominations for the given change amount.
// (https://andrew.neitsch.ca/publications/m496pres1.nb.pdf)
//
// I would give my client this option in reality, but explain that this would require some extensive
// research on my part. Rather than taking the time to implement that solution, I used the algorithm
// of choosing a denomination at random and subracting a random amount of the denomination it from
// the change, until I account for all the change.
public Dictionary <CashDenominations, int> CalculateRandomAmountsOfChange(CashTransaction cashTransaction)
{
Dictionary <CashDenominations, int> result = new Dictionary <CashDenominations, int>();
int remainderOfChange = cashTransaction.ChangeTotal;
List <CashDenominations> cashDenominations =
Enum.GetValues(typeof(CashDenominations))
.Cast <CashDenominations>()
.ToList();
while (remainderOfChange > 0)
{
int randomDenominationIndex = Random.Next(cashDenominations.Count);
CashDenominations randomDenomination = cashDenominations[randomDenominationIndex];
int randomDenominationAsInt = (int)randomDenomination;
if (randomDenominationAsInt <= remainderOfChange)
{
int randomAmoutOfTheDenomination =
Random.Next(1, remainderOfChange / randomDenominationAsInt + 1);
remainderOfChange -= randomDenominationAsInt * randomAmoutOfTheDenomination;
// See if denom has entry, if not, add + make value 1
// If so, increment the value.
if (result.ContainsKey(randomDenomination))
{
result[randomDenomination] += randomAmoutOfTheDenomination;
}
else
{
result.Add(randomDenomination, randomAmoutOfTheDenomination);
}
}
}
return(result);
}
// Minimum and random calculations are in separate functions for readability and
// testing.
public Dictionary <CashDenominations, int> CalculateMinimumAmountsOfChange(CashTransaction cashTransaction)
{
Dictionary <CashDenominations, int> result = new Dictionary <CashDenominations, int>();
int remainderOfChange = cashTransaction.ChangeTotal;
CashDenominations[] cashDenominationsSortedFromGreatestToLeast =
Enum.GetValues(typeof(CashDenominations))
.Cast <CashDenominations>()
.Reverse <CashDenominations>()
.ToArray <CashDenominations>();
foreach (CashDenominations cashDenomination in cashDenominationsSortedFromGreatestToLeast)
{
int cashDenominationAsInt = (int)cashDenomination;
int denominationCount = remainderOfChange / cashDenominationAsInt;
result.Add(cashDenomination, denominationCount);
if (remainderOfChange > cashDenominationAsInt)
{
remainderOfChange %= cashDenominationAsInt;
}
}
return(result);
}