/// <summary>
/// retreive a specific lexical premutation
/// </summary>
/// <param name="workingNumberToFind"></param>
/// <returns></returns>
public string GetPremutation(long numberToFind)
{
string result = null;
string startingSequence = originalSequence;
long workingNumberToFind = numberToFind;
for (long digit = 0; digit < originalSequence.Length - 1; digit++)
{
long factorial = MathLibrary.Factorial(originalSequence.Length - digit - 1);
long position = workingNumberToFind / factorial;
long remainder = workingNumberToFind % factorial;
if (remainder > 0)
{
position++;
}
result = result + startingSequence.Substring((int)position - 1, 1);
startingSequence = startingSequence.Remove((int)position - 1, 1);
long factorialBorder = (position - 1) * factorial;
workingNumberToFind = workingNumberToFind - factorialBorder;
}
return(result + startingSequence);
}
/// <summary>
/// Create premutations based on an array of digits
/// </summary>
/// <param name="things"></param>
public Premutations(long[] things)
{
this.things = things;
count = MathLibrary.Factorial(things.Length);
originalSequence = null;
foreach (long digit in things)
{
originalSequence = digit.ToString() + originalSequence;
}
}
/// <summary>
/// Create premutations based on a list of digits
/// </summary>
/// <param name="things"></param>
public Premutations(List <long> things)
{
this.things = things.ToArray <long>();
count = MathLibrary.Factorial(things.Count);
originalSequence = null;
foreach (long digit in things)
{
originalSequence = digit.ToString() + originalSequence;
}
}
/// <summary>
/// Create premutations base on a string of digits
/// </summary>
/// <param name="things"></param>
public Premutations(string things)
{
this.originalSequence = things;
count = MathLibrary.Factorial(things.Length);
}
