public static List <T[]> GetPermutation(T[] t, int startIndex, int endIndex)
{
if (startIndex < 0 || endIndex > t.Length - 1)
{
return(null);
}
List <T[]> result = new List <T[]>();
PermutationAndCombination <T> .GetPermutation(ref result, t, startIndex, endIndex);
return(result);
}
public static List <T[]> GetCombination(T[] t, int n)
{
if (t.Length < n)
{
return(null);
}
int[] b = new int[n];
List <T[]> result = new List <T[]>();
PermutationAndCombination <T> .GetCombination(ref result, t, t.Length, n, b, n);
return(result);
}
public static List <T[]> GetPermutation(T[] t, int n)
{
if (n > t.Length)
{
return(null);
}
List <T[]> list = new List <T[]>();
List <T[]> combination = PermutationAndCombination <T> .GetCombination(t, n);
for (int i = 0; i < combination.Count; i++)
{
List <T[]> collection = new List <T[]>();
PermutationAndCombination <T> .GetPermutation(ref collection, combination[i], 0, n - 1);
list.AddRange(collection);
}
return(list);
}
private static void GetPermutation(ref List <T[]> list, T[] t, int startIndex, int endIndex)
{
if (startIndex == endIndex)
{
if (list == null)
{
list = new List <T[]>();
}
T[] array = new T[t.Length];
t.CopyTo(array, 0);
list.Add(array);
return;
}
for (int i = startIndex; i <= endIndex; i++)
{
PermutationAndCombination <T> .Swap(ref t[startIndex], ref t[i]);
PermutationAndCombination <T> .GetPermutation(ref list, t, startIndex + 1, endIndex);
PermutationAndCombination <T> .Swap(ref t[startIndex], ref t[i]);
}
}
private static void GetCombination(ref List <T[]> list, T[] t, int n, int m, int[] b, int M)
{
for (int i = n; i >= m; i--)
{
b[m - 1] = i - 1;
if (m > 1)
{
PermutationAndCombination <T> .GetCombination(ref list, t, i - 1, m - 1, b, M);
}
else
{
if (list == null)
{
list = new List <T[]>();
}
T[] array = new T[M];
for (int j = 0; j < b.Length; j++)
{
array[j] = t[b[j]];
}
list.Add(array);
}
}
}
public static List <T[]> GetPermutation(T[] t)
{
return(PermutationAndCombination <T> .GetPermutation(t, 0, t.Length - 1));
}
