This is a solution to problem 3 on the hard interview questions node. If you have not read the question, the following will make no sense to you:

First, reverse the whole string (by swapping the first and the last character, towards the middle, etc). This should be enough of a hint to get you started. If not, read on:

Then reverse the order of the characters in each word. Now the characters in each word are in the original order (they were reversed twice overall), but the words are in reverse order (the first word is now at the end, etc.)