public string Compute()
{
long result = 0;
string digits = null;
for (int digit = 1; digit <= 9; digit++)
{
digits += digit.ToString();
Premutations premutations = new Premutations(digits);
for (int index = 1; index <= premutations.Count(); index++)
{
string premutation = premutations.GetPremutation(index);
long candidate = long.Parse(premutation);
if (candidate > result)
{
if (MathLibrary.IsPrime(candidate))
{
result = candidate;
}
}
}
}
return(result.ToString());
}
public string Compute()
{
List <long> primeNumbers = MathLibrary.GetPrime(9999);
for (long candidate = 1000; candidate <= 9999; candidate++)
{
if (candidate.Equals(1487) | candidate.Equals(4817) | candidate.Equals(8147))
{
continue; // ignore the sample case
}
if (!primeNumbers.Contains(candidate))
{
continue; // ignore when the first number is not prime
}
string startSequence = candidate.ToString();
Premutations premutations = new Premutations(startSequence);
for (long index1 = 2; index1 < premutations.Count(); index1++)
{
for (long index2 = index1 + 1; index2 <= premutations.Count(); index2++)
{
string secondString = premutations.GetPremutation(index1);
long secondNumber = long.Parse(secondString);
if (candidate == secondNumber)
{
continue; // ignore if the first and second are the same
}
if (!primeNumbers.Contains(secondNumber))
{
continue; // ignore if the second is not prime
}
string thirdString = premutations.GetPremutation(index2);
long thirdNumber = long.Parse(thirdString);
if (candidate == thirdNumber)
{
continue; // Ignore if the first and third are the same
}
if (!primeNumbers.Contains(thirdNumber))
{
continue; // Ignore if the third number is not prime
}
if (secondNumber != thirdNumber)
{
if (Math.Abs(secondNumber - candidate) == Math.Abs(thirdNumber - secondNumber))
{
return(candidate + secondString + thirdString);
}
}
}
}
}
return(null);
}
public string Compute()
{
long result = 0;
Premutations premutations = new Premutations("0123456789");
for (long index = 1; index <= premutations.Count(); index++)
{
string premutation = premutations.GetPremutation(index);
if (long.Parse(premutation.Substring(1, 3)) % 2 > 0)
{
continue;
}
if (long.Parse(premutation.Substring(2, 3)) % 3 > 0)
{
continue;
}
if (long.Parse(premutation.Substring(3, 3)) % 5 > 0)
{
continue;
}
if (long.Parse(premutation.Substring(4, 3)) % 7 > 0)
{
continue;
}
if (long.Parse(premutation.Substring(5, 3)) % 11 > 0)
{
continue;
}
if (long.Parse(premutation.Substring(6, 3)) % 13 > 0)
{
continue;
}
if (long.Parse(premutation.Substring(7, 3)) % 17 > 0)
{
continue;
}
result += long.Parse(premutation);
}
return(result.ToString());
}
