public IEnumerable<IEnumerable<int>> GetResults(BooleanMatrix pairs, int count, ImmutableSequence<int> current)
{
int length = pairs.Width;
int start;
if (!current.HasValue)
{
start = 0;
}
else
{
start = current.First();
}
var results = new Range(start, length)
.Where(i => current
.All(x => pairs[x, i]));
if (count == 1)
{
return results
.Select(i => new ImmutableSequence<int>(i, current));
}
else
{
return results
.SelectMany(i => GetResults(pairs, count - 1, new ImmutableSequence<int>(i, current)));
}
}
public override object CalculateResult()
{
int maximum = 10000;
long[] primes = PrimeGenerator.Instance
.TakeWhile(p => p < maximum)
.ToArray();
int length = primes.Length;
var pairs = new BooleanMatrix(length, length);
for (int i = 0; i < length; i++)
{
long alpha = primes[i];
long alphaMultiplier = MathUtilities.Pow(10, (long)Math.Log10(alpha) + 1);
for (int j = i + 1; j < length; j++)
{
long bravo = primes[j];
if (PrimeGenerator.Instance.IsPrime(bravo * alphaMultiplier + alpha) &&
PrimeGenerator.Instance.IsPrime(alpha * MathUtilities.Pow(10, (long)Math.Log10(bravo) + 1) + bravo))
{
pairs[i, j] = true;
pairs[j, i] = true;
}
}
}
return GetResults(pairs, 5, ImmutableSequence<int>.Empty)
.Select(g => g
.Select(p => primes[p])
.Sum())
.Min();
}
public BooleanMatrix(BooleanMatrix source)
{
if (source == null)
{
throw new ArgumentNullException("source");
}
_width = source._width;
_height = source._height;
byte[] sourceData = source._data;
int length = sourceData.Length;
_data = new byte[length];
for (int i = 0; i < length; i++)
{
_data[i] = sourceData[i];
}
}