public void FactorUtils_GetFactors_28()
{
AssertEqual(new long[] { 1, 2, 4, 7, 14, 28 }, FactorUtils.GetFactors((long)28));
}
public void FactorUtils_GetFactors_2()
{
AssertEqual(new long[] { 1, 2 }, FactorUtils.GetFactors((long)2));
}
public void FactorUtils_GetFactors_10()
{
AssertEqual(new long[] { 1, 2, 5, 10 }, FactorUtils.GetFactors((long)10));
}
private static Dictionary <int, int> GetFactorSumDict(int n)
{
return(Enumerable.Range(2, n - 2)
.Select(i => new { i, FactorSum = (int)FactorUtils.GetProperFactors(i).Sum() })
.ToDictionary(a => a.i, a => a.FactorSum));
}
public void FactorUtils_GetFactors_1()
{
AssertEqual(new long[] { 1 }, FactorUtils.GetFactors((long)1));
}
public static bool IsAbundant(this int n)
{
return(FactorUtils.GetProperFactors(n).Sum() > n);
}
public static bool IsPerfect(this int n)
{
return(FactorUtils.GetProperFactors(n).Sum() == n);
}
public static bool IsDeficient(this int n)
{
return(FactorUtils.GetProperFactors(n).Sum() < n);
}
public static long AmicableSumUnderN(int n)
{
var factorSumDict = Enumerable.Range(2, n - 2).Select(i => new { i, FactorSum = (int)FactorUtils.GetProperFactors(i).Sum() })
.Where(p => p.FactorSum > 1).ToDictionary(a => a.i, a => a.FactorSum);
var amicableNumbers = factorSumDict
.Where(d => factorSumDict.ContainsKey(d.Value) && d.Key == factorSumDict[d.Value] && d.Key != d.Value)
.SelectMany(i => new[] { i.Key, i.Value }).Distinct().ToList();
return(amicableNumbers.Sum());
}
public static long TriangleNumberWithNDivisors(int n)
{
return(TriangleNumberUtils.TriangleNumbers.SkipWhile(t => FactorUtils.GetFactors(t).Count() < n).First());
}