// A number n is called called abundant if sum of its proper divisors exceeds n.
public long GetNonabundantsum(int to)
{
//lag liste av aktuelle AbundantNumber
var abundantNumbersListe = Enumerable.Range(1, to).Where(i => Divisors.IsAbundantNumber(i)).ToList();
//lag hashmap av AbundantNumber listen
var abundantNumbersDictionary = abundantNumbersListe.ToDictionary(e => e);
//finn summen
//er i= a+b hvor a og b er AbundantNumber ? , ellers legg til sum
long nonabundantsum = 0;
for (int i = 1; i <= to; i++)
{
if (
abundantNumbersListe
.Where(e => e < i)
.Where(a => abundantNumbersDictionary.ContainsKey(i - a))
.FirstOrDefault() == 0 //hvis ikke i kan skrives som summen av to tall i abundantNumbersListe
)
{
nonabundantsum += i;
}
}
return(nonabundantsum);
}
public void Test1()
{
/*
* As 12 is the smallest abundant number, 1 + 2 + 3 + 4 + 6 = 16,
* the smallest number that can be written as the sum of two abundant numbers is 24.
*/
Assert.True(Divisors.IsAbundantNumber(12));
var sut = new E023Nonabundantsums();
long nonabundantsumExpected = 276;
long nonabundantsum = sut.GetNonabundantsum(to: 23);
Assert.Equal(nonabundantsumExpected, nonabundantsum);
//24 kan skrive som sum
nonabundantsum = sut.GetNonabundantsum(to: 24);
Assert.Equal(nonabundantsumExpected, nonabundantsum);
}