Code Cracker is a puzzle that appears in the Otago Daily Times. It is like a crossword, in that it is a rectangular area with words running horizontally and vertically, which you have to recover from clues. There is a mapping from the integers 1–26 to the letters A–Z which you have to recover. You are given the answer for some of the numbers.
This program works by using a large dictionary of English words. It takes each clue in turn, and finds all the dictionary words of the right length that are consistent with that clue and with what's already been solved. If there are no such words, we're out of luck. (This can happen because the word you need is not in the dictionary.) If there's exactly one such word, we've solved that clue completely and can cross it off. If there's more than one such word, we glean what we can (e.g., if it could be CLANGER or CLINGER then at least it's CL-NGER, but we'll have to finish it later.