https://github.com/ebowman/wordsnake

Solves the "wordsnake" puzzle
https://github.com/ebowman/wordsnake

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Solves the "wordsnake" puzzle

• Host: GitHub
• URL: https://github.com/ebowman/wordsnake
• Owner: ebowman
• Created: 2012-05-02T22:26:30.000Z (over 12 years ago)
• Default Branch: master
• Last Pushed: 2012-05-03T18:23:24.000Z (over 12 years ago)
• Last Synced: 2023-04-19T17:17:25.644Z (over 1 year ago)
• Language: Scala
• Size: 102 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
wordsnake

=========

Solves the "wordsnake" puzzle.

Brute-force solves the "wordsnake" problem. Wordsnakes are the different ways

one can combine words together using as few letters as possible.  For example,

"terrible" and "english" have two (ordered) wordsnakes: "terribleenglish" and

"terriblenglish".  For the wordsnakes problem, we take a list of words and

compute all the smallest ways to combine them.

This is in essence a travelling salesman problem, which is ultimately a problem in permutations.

In this program we consider all permutations of the list of words, and fold over the permutation

a merge operation that finds the shortest wordsnake for each adjacent pair of words, so that we end

up with the smallest wordsnake for each permutation.  When then iterate over all permutations and

remember the best paths.

One interesting aspect of this program from a scala point of view, is how it uses a lazy iterator over

the permutations, and a fold operation (instead of foldLeft).  The fold works over a parallel collection,

so we pull off some number of permutations from the iterator, and then do the parallel fold over them.

It took some experimentation to find the right value for "pageSize", the number to pull of the iterator

in one go.

This program runs fastest without about a 500M heap, though will run fine (slightly slower) with a much

smaller heap; I ran it with a 5M heap to completion (though much slower than with a bigger heap).

$ scala -cp target/scala-2.9.1/classes -J-Xms5m -J-Xmx5m -J-server Main

This idea was taken from _Puzzles for Programmers and Pros_ by Dennis E. Sasha, Wiley Publishing, Indianapolis,

(c) pp.171-173