public static uint CountWaysToMakeChange(this Money money, params Denomination[] denominations)
{
Positive.Amounts.AssertArgument(nameof(money), money.Amount);
Guard.AgainstNullArgument(nameof(denominations), denominations);
long n = money.MinorIntegralAmount;
int m = denominations.Length;
Currency operationCurrency = money.GetCurrency();
long[] integralDenominations = denominations
.Select(d => IntegralDenomination.CalculateAmount(d, operationCurrency))
.ToArray();
// table[i] will be storing the number of solutions for value i.
// n+1 rows are needed since the table is constructed in bottom up manner using the base case (n = 0)
uint[] table = new uint[n + 1];
// Base case (If given value is 0)
table[0] = 1u;
// Pick all denominations one by one and update the table[] values after the index
// greater than or equal to the value of the picked coin
for (int i = 0; i < m; i++)
{
for (long j = integralDenominations[i]; j <= n; j++)
{
table[j] += table[j - integralDenominations[i]];
}
}
return(table[n]);
}
internal OptimalChangeSolution(long toChange, Currency operationCurrency, ushort[] table, IntegralDenomination?[] usedDenominations)
{
_denominations = new QuantifiedDenomination[0];
ushort possibleSolution = table.Last();
if (possibleSolution != ushort.MaxValue)
{
// at most as many denominations as used
List <Denomination> denominations = new List <Denomination>(usedDenominations.Length);
IntegralDenomination defaultDenomination = IntegralDenomination.Default(operationCurrency);
long denomination = toChange;
while (denomination > 0)
{
IntegralDenomination usedDenomination = usedDenominations[denomination]
.GetValueOrDefault(defaultDenomination);
denominations.Add(usedDenomination.Denomination);
denomination -= usedDenomination.IntegralAmount;
}
_denominations = QuantifiedDenomination.Aggregate(denominations.OrderByDescending(d => d.Value))
.ToArray();
}
}