public int NumberOfDivisors(long number)
{
int numberOfDivisors = 1;
List <int> primeFactors = _primeService.GetPrimeFactors(number).ToList();
// number of divisors d(n) = (a+1)(b+1)(c+1)...
// where n = p^a * q^b * r^c ... (expressed as a product of prime factors)
while (primeFactors.Count > 0)
{
int a = primeFactors[0];
primeFactors.RemoveAt(0);
int countOfA = 1;
// Remove all other occurences of a.
while (true)
{
if (primeFactors.Contains(a))
{
++countOfA;
primeFactors.Remove(a);
continue;
}
break;
}
numberOfDivisors *= countOfA + 1;
}
return(numberOfDivisors);
}
public override string GetAnswer()
{
var numbers = new Queue <List <int> >();
numbers.Enqueue(_primeService.GetPrimeFactors(1).ToList());
numbers.Enqueue(_primeService.GetPrimeFactors(2).ToList());
numbers.Enqueue(_primeService.GetPrimeFactors(3).ToList());
for (int i = 4; ; ++i)
{
List <int> newFactors = _primeService.GetPrimeFactors(i).ToList();
CondenseDuplicates(newFactors);
numbers.Enqueue(newFactors);
bool found = true;
foreach (List <int> factors in numbers)
{
if (factors.Count != 4)
{
found = false;
break;
}
}
if (found)
{
break;
}
numbers.Dequeue();
}
List <int> primeFactors = numbers.Dequeue();
int product = 1;
foreach (int factor in primeFactors)
{
product *= factor;
}
return(product.ToString());
}