public static double Run()
{
Console.WriteLine("Project Euler - 27: Quadratic primes");
var r = 0d;
var z = 1d;
for (var a = -999; a < 1000; a++)
{
for (var b = -999; b < 1000; b++)
{
for (var n = 0; ; n++)
{
if (!Helpers.IsPrime(n * n + a * n + b))
{
if (n > z)
{
r = a * b;
z = n;
}
break;
}
}
}
}
return(r);
}
static bool IsTruncatablePrime(int n)
{
if (n % 2 == 0 || n % 10 == 5 || n % 10 == 9 || n % 10 == 1 || (n % 100) % 3 == 0 || (n % 1000) % 3 == 0 || (n % 10000) % 3 == 0)
{
return(false);
}
var s = n.ToString();
// The Reason I couldnt find a solution earlier was because I added "2" and "5" to this iist, which excludes the very valid numbers 23 and 53
if (s.Contains("0") || s.Contains("4") || s.Contains("6") || s.Contains("8"))
{
return(false);
}
foreach (var i in Truncate(n))
{
if (!Helpers.IsPrime(i))
{
return(false);
}
}
return(true);
}
public static double Run()
{
Console.WriteLine("We're just starting out baby. Project Euler - 3");
var r = 600851475143d;
for (var i = 5d; i < Math.Sqrt(r); i += 2)
{
if (Helpers.IsPrime((int)i))
{
while (r % i == 0)
{
r /= i;
}
}
}
return(r);
}
