Algorithm to permute elements in Array

Answer 1

This looks like you want to generate permutations of your list in lexical order. Those search terms should start you on a useful path.

For instance, Python includes this in the itertools module from version 2.6 on. That documentation shows code that implements such an algorithm.

Answer 2

This gives you next permutation:

bool Increase(int[] values) {
   // locate the last item which is smaller than the following item
   int pos = values.Length - 2;
   while (pos >= 0 && values[pos] > values[pos + 1]) pos--;
   // if not found we are done
   if (pos == -1) return false;
   // locate the item next higher in value
   int pos2 = values.Length - 1;
   while (values[pos2] < values[pos]) pos2--;
   // put the higher value in that position
   int temp = values[pos];
   values[pos] = values[pos2];
   values[pos2] = temp;
   // reverse the values to the right
   Array.Reverse(values, pos + 1, values.Length - pos - 1);
   return true;
}

Edit:
Changed Array.Sort to Array.Reverse. The items are always in descending order and should be in ascending order, so they give the same result.