private static bool GenerateString(LinkedList <int> soFar, HashSet <int> codes)
{
Console.WriteLine(soFar.Count);
if (soFar.Count == (3 + Math.Pow(NumDigitsInCode, 4)))
{
return(true);
}
if (soFar.Count < 3)
{
for (int i = 0; i < LockStringGenerator.NumDigitsInCode; i++)
{
soFar.AddLast(i);
if (LockStringGenerator.GenerateString(soFar, codes))
{
return(true);
}
soFar.RemoveLast();
}
return(false);
}
// We need to try tacking on all digits that give us new codes.
for (int i = 0; i < LockStringGenerator.NumDigitsInCode; i++)
{
int newCode = GetNewCode(soFar, i);
if (!codes.Contains(newCode))
{
codes.Add(newCode);
soFar.AddLast(i);
if (LockStringGenerator.GenerateString(soFar, codes))
{
return(true);
}
soFar.RemoveLast();
codes.Remove(newCode);
}
}
return(false);
}
// Try by generating all permutations. There are 10,000 unique codes.
// The optimal string is of length 10,003 because the first code is of
// length 4 and then each additional appended digit generates a new unique code,
// so 4 + 9,999 = 10,003.
public static string GenerateString()
{
LinkedList <int> result = new LinkedList <int>();
if (LockStringGenerator.GenerateString(result, new HashSet <int>()))
{
StringBuilder rval = new StringBuilder();
foreach (int i in result)
{
rval.Append(i);
}
return(rval.ToString());
}
else
{
return(null);
}
}