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From "Luc Maisonobe (JIRA)" <>
Subject [jira] [Commented] (COLLECTIONS-404) Adding an implementation of Eugene Myers difference algorithm
Date Sun, 28 Apr 2013 19:04:16 GMT


Luc Maisonobe commented on COLLECTIONS-404:

No, sorry, I am not able to confirm it.
When we wrote this almost 10 years ago, we had several issues with indexes (starting at 0
versus starting at 1, with the additional difficulty of reversed numbering when building the
half snake from the end).

So I guess there are several parts were we appear to differ from the paper, but in fact we
don't. The final fixes we made were by stepping in the code with debugger with the various
test cases. Does the change you propose still work with the existing test cases?
> Adding an implementation of Eugene Myers difference algorithm
> -------------------------------------------------------------
>                 Key: COLLECTIONS-404
>                 URL:
>             Project: Commons Collections
>          Issue Type: Improvement
>          Components: Collection
>    Affects Versions: 3.2.1
>         Environment: all
>            Reporter: Luc Maisonobe
>            Priority: Minor
>             Fix For: 4.0
>         Attachments: commons-collections-difference.patch, commons-collections-difference-v2.patch,
> The difference algorithm aims at comparing two sequences of objects and return an "edit
script" which represents how one can transform the first sequence into the second sequence.
The script describes the various insert object, delete object and keep object commands. The
script is guaranteed to be the shortest possible in terms of number of commands.
> From the script, one can either extract longest common sub-sequences (i.e. how similar
the sequences are) or on the contrary the needed changes (i.e. how different the sequences

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