public string Run()
{
var factorizations = Prime.Factorization.Of(Enumerable.Range(1, 10000000).Select(i => (long)i));
var facAsList = new Prime.Factorization[10000001];
foreach (var fac in factorizations)
{
facAsList[(int)fac.Key] = fac.Value;
}
int run = 0;
int curr = 1;
while (run != 4)
{
if (facAsList[curr].Values.Count() == 4)
{
run++;
}
else
{
run = 0;
}
curr++;
}
return((curr - 4).ToString());
}
private (bool possible, Prime.Factorization higher, Prime.Factorization lower) FindConsecutiveFactorizations(long number)
{
var factorization = new Prime.Factorization();
var high = number % 2 == 1 ? number : number - 1;
var low = number % 2 == 1 ? (number - 1) / 2 : number / 2;
var product = Prime.Factorization.Of(high).MultiplyBy(low);
var exponentList = product.ToList();
(bool possible, Prime.Factorization higher, Prime.Factorization lower) FactorizationInternal(Prime.Factorization current, int primeIndex)
{
if (primeIndex >= exponentList.Count)
{
return(false, null, null);
}
var withPrimeSkipped = FactorizationInternal(current, primeIndex + 1);
if (withPrimeSkipped.possible)
{
return(withPrimeSkipped);
}
var(prime, exp) = exponentList[primeIndex];
for (int i = 1; i <= exp; i++)
{
current.MultiplyByPrime(prime);
var currentValue = current.Value();
if (currentValue >= high)
{
current.DivideByPrime(prime);
break;
}
if (currentValue > low)
{
var other = new Prime.Factorization(product);
var dividend = other.DivideBy(current);
var dividendValue = dividend.Value();
if (dividendValue == current.Value() + 1)
{
return(true, dividend, current);
}
if (dividendValue == currentValue - 1)
{
return(true, current, dividend);
}
current.DivideByPrime(prime);
break;
}
var withPrime = FactorizationInternal(current, primeIndex + 1);
if (withPrime.possible)
{
return(withPrime);
}
current.DivideByPrime(prime);
}
return(false, null, null);
}
return(FactorizationInternal(factorization, 0));
}
