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

This is a variation for the problem "Hello world" becomes "world Hello" the only difference is that you don't need to do the initial swaping.

 public string Reverse(string words)
        {
            char[] letters = words.ToCharArray();
           // letters = ReverseLetters(letters, 0, letters.Length - 1); // No need for this one

            int start = 0;

            while (start < letters.Length)
            {
                if (letters[start] !=' ')
                {
                    int end = start;
                    while (end < letters.Length && letters[end] != ' ')
                        end++;
                    end--;
                    letters = ReverseLetters(letters, start, end);
                    start = end;
                }
                start++;
            }

            return new String(letters);
        }

        private char[] ReverseLetters(char[] letters,int start ,int end)
        {
            while(start < end)
            {
                char temp = letters[end];
                letters[end] = letters[start];
                letters[start] = temp;
                start++;
                end--;
            }
            return letters;
        }