title: Generating power set recursively without any loops
body: <p>How do you write a recursive method PowerSet(String input) that prints out all possible combinations of a string that is passed to it?</p>
  
  <p>For example: PowerSet("abc") will print out abc, ab, ac, bc, a, b, c</p>
  
  <p>I have seen some recursive solutions with loops, but in this case no loops are allowed. </p>
  
  <p>Any ideas?</p>
  
  <p>Edit: The required method has only one parameter, i.e. String input.</p>