Word Ladders - Medium

Word ladder is a word game invented by Lewis Carroll. A word ladder puzzle begins with two words, and to solve the puzzle one must find a chain of other words to link the two, in which two adjacent words (that is, words in successive steps) differ by one letter. Eg. SPORT <-> SHORT

Source: Wikipedia

If you've followed my previous Dijkstra's Shortest Path Algorithm Tutorial, you'll be able to solve this challenge with minimum effort.

Essentially, we create a graph where each word is a vertex and there exists an edge if two words differ by a single character. To find the word ladder is basically running any shortest path algorithm. You could also use a Breadth First Search.

Some important observations

The length of the source and destination words must be the same for a path to exist.
The path from source to destination can only contain words of the same length. So we can prune off the rest of the dictionary.
The graph is undirected.

Here's my implementation, it uses the modules from the tutorial.

To run the program, "wordladder.py SOURCE DESTINATION < dict.txt"
For eg.

C:\>wordladder.py BOX TEN < words.txt
(4, ['BOX', 'BOD', 'BED', 'BEN', 'TEN'])

Comments

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