public void InverseFactorTest()
{
for (var i = 1; i < 1000; i++)
{
var powers = PrimeFactors.Factor(i);
Assert.That(PrimeFactors.Value(powers), Is.EqualTo(i));
}
}
/// <summary>
/// Generate an iterator over the divisors of the number whose prime
/// factorization has been passed in, other than the number itself.
/// Iteration will proceed as for <see cref="Divisors(int[])"/>.
/// </summary>
/// <param name="factors">Prime factors of the value whose divisors are desired</param>
/// <returns>An enumerator over all proper divisors of the number.</returns>
public static IEnumerable <int> ProperDivisors(int[] factors)
{
var value = PrimeFactors.Value(factors);
foreach (var i in Divisors(factors))
{
if (i < value)
{
yield return(i);
}
}
}
/// <summary>
/// Get the perfection of a number. A number whose proper divisors
/// add up to the number is called "perfect". If the sum is less then the
/// number it is called "deficient". Otherwise it is called "abundant".
/// </summary>
/// <param name="factors">Prime factor powers of the number</param>
/// <returns>-1 if deficient, 0 if perfect, 1 if abundant</returns>
public static int Perfection(int[] factors)
{
var sum = 0;
var value = PrimeFactors.Value(factors);
foreach (var i in ProperDivisors(factors))
{
sum += i;
if (sum > value)
{
return(1);
}
}
return((sum < value) ? -1 : 0);
}
public void InverseFactorValue(int value)
{
var powers = PrimeFactors.Factor(value);
Assert.That(PrimeFactors.Value(powers), Is.EqualTo(value));
}