protected override string Solve()
{
int result = 0;
IEnumerable <long> primes = PrimeHelper.GeneratePrimes(999999);
foreach (long prime in primes)
{
IEnumerable <long> rotations = NumberHelper.GetRotations(prime);
int primeCount = 0;
foreach (long rotation in rotations)
{
if (PrimeHelper.IsPrime(rotation))
{
primeCount++;
}
}
if (primeCount == rotations.Count())
{
result++;
}
}
return(result.ToString("0"));
}
protected override string Solve()
{
long result = 0;
IEnumerable <long> primes = PrimeHelper.GeneratePrimes(1999999);
result = primes.Sum();
return(result.ToString("0"));
}
protected override string Solve()
{
//stab in the dark here, the 10001st prime is probably below 10million?
//could check numbers incrementally as prime or not, but a Sieve would be faster still
IList <long> primes = PrimeHelper.GeneratePrimes(10000000).ToList();
primes.OrderBy(o => o);
return(primes[10000].ToString("0"));
}
protected override string Solve()
{
int hitCount = 0;
int result = 0;
IList <long> primes = PrimeHelper.GeneratePrimes(100000000).ToList();
primes.Remove(2);
primes.Remove(3);
primes.Remove(5);
primes.Remove(7);
for (int i = 0; i < primes.Count; i++)
{
bool primeCheck = true;
int n = i;
//check primality right to left
do
{
if (PrimeHelper.IsPrime(n) == false)
{
primeCheck = false;
break;
}
n /= 10;
} while (n > 0);
//check primality left to right
if (primeCheck) //don't bother if already failed right to left
{
n = i;
int modulo = (int)Math.Pow(10, (NumberHelper.GetDigits(n).Count() - 1));
do
{
n %= modulo;
modulo = (int)Math.Pow(10, (NumberHelper.GetDigits(n).Count() - 1));
if (PrimeHelper.IsPrime(n) == false)
{
primeCheck = false;
break;
}
} while (modulo != 1);
}
if (primeCheck)
{
result += i;
hitCount++;
}
if (hitCount == 11)
{
return(result.ToString("0"));
}
}
return("none found");
}