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https://github.com/markus1189/anagramskata

The Anagrams Kata from Dave Thomas
https://github.com/markus1189/anagramskata

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The Anagrams Kata from Dave Thomas

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README 

        
### Kata Six: Anagrams



Back to non-realistic coding this week (sorry, Martin). Let's solve some

crossword puzzle clues.



In England, I used to waste hour upon hour doing newspaper crosswords.

As crossword fans will know, English cryptic crosswords have a totally

different feel to their American counterparts: most clues involve

punning or word play, and there are lots of anagrams to work through.

For example, a recent Guardian

[crossword](http://www.guardian.co.uk/crossword/java/blank/0,7082,-5903,00.html)

had:



      Down:

        ..

        21. Most unusual form of arrest (6)



The hint is the phrase ‘form of,’ indicating that we’re looking for an

anagram. Sure enough ‘arrest’ has six letters, and can be arranged

nicely into ‘rarest,’ meaning ‘most unusual.’ (Other anagrams include

raster, raters, Sartre, and starer)



A while back we had a thread on the Ruby mailing list about finding

anagrams, and I’d like to resurrect it here. The challenge is fairly

simple: given a file containing one word per line, print out all the

combinations of words that are anagrams; each line in the output

contains all the words from the input that are anagrams of each other.

For example, your program might include in its output:



      kinship pinkish

      enlist inlets listen silent

      boaster boaters borates

      fresher refresh

      sinks skins

      knits stink

      rots sort



If you run this on the word list

[here](http://pragdave.pragprog.com/data/wordlist.txt) you should find

2,530 sets of anagrams (a total of 5,680 words). Running on a larger

dictionary (about 234k words) on my OSX box produces 15,048 sets of

anagrams (including all-time favorites such as actaeonidae/donatiaceae,

crepitant/pittancer, and (for those readers in Florida)

electoral/recollate).



For added programming pleasure, find the longest words that are

anagrams, and find the set of anagrams containing the most words (so

"parsley players replays sparely" would not win, having only four words

in the set).



Kata Objectives

---------------



Apart from having some fun with words, this kata should make you think

somewhat about algorithms. The simplest algorithms to find all the

anagram combinations may take inordinate amounts of time to do the job.

Working though alternatives should help bring the time down by orders of

magnitude. To give you a possible point of comparison, I hacked a

solution together in 25 lines of Ruby. It runs on the word list from my

web site in 1.5s on a 1GHz PPC. It’s also an interesting exercise in

testing: can you write unit tests to verify that your code is working

correctly before setting it to work on the full dictionary.



Posted at 05:56 PM |

[Permalink](http://codekata.pragprog.com/2007/01/kata_six_anagra.html)