Interview Question for Software Development Engineer In Test (SDET) II at Microsoft:

- Reverse the array from 0 to array length
- Reverse the array from position 0 to n and n+1 to array length
- When doing the reverse (swapping elements) it can be done with no extra space using XOR

 public string RotateOnIndex(string word, int index)
            {
                if (String.IsNullOrWhiteSpace(word))
                    return word;

                if (index < 0 || index > (word.Length - 1))
                    return String.Empty;

                char[] letters = word.ToCharArray();

                Reverse(letters, 0, letters.Length - 1);

                Reverse(letters, index, letters.Length - 1);

                Reverse(letters, 0, index - 1);

                return new String(letters);
            }

            private void Reverse(char[] letters, int start, int end)
            {
                while (start < end)
                {
                    letters[start] ^= letters[end];
                    letters[end] ^= letters[start];
                    letters[start] ^= letters[end];
                    start++;
                    end--;
                }
            }