Groups > comp.lang.java.programmer > #14787

Re: Patricia trie vs binary search.

From	markspace <-@.>
Newsgroups	comp.lang.java.programmer
Subject	Re: Patricia trie vs binary search.
Date	2012-05-24 17:56 -0700
Organization	A noiseless patient Spider
Message-ID	<jpmlbf$a3o$1@dont-email.me> (permalink)
References	<jpmev4$63l$1@dont-email.me> <jpmgrb$o5a$1@speranza.aioe.org>

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On 5/24/2012 4:39 PM, glen herrmannsfeldt wrote:
> markspace<-@.>  wrote:
>> For some reason I was thinking about sub-string searches today.  I
>> looked up Patricia tries (a kind of radix tree) to see if they would
>> help.  While interesting, the radix tree seems to have a lot of overhead
>> for large numbers of entries.
>
> I am not so sure which substring problem you are interested in,
> but you might look at the Aho-Korasick algorithm.
>
> If you want to allow for insertions and/or deletions, look
> at dynamic programming.

Thanks for those pointers (pun not intended).  The "sub-string search" 
was referring to was picking words out of a longer, undelimited string.

The example I posted looked for bad passwords within a larger password.

"passxword" contains at least two bad passwords, pass and word, 
according to the dictionary file I download from here (that's the 
bpw.txt file in the sample code):

<http://www.godlikeproductions.com/badpasswords.php>

The code I posted find pass, ass, word, and or in the string 
"passxword", which are all bad passwords according to that link above. 
(I deliberately avoid reporting single letters as bad).

Practically speaking, hashing appears to be just as fast for a lookup, 
but hashing doesn't tell you when to stop, so it's always N^2 for this 
sort of problem.  My algorithm should average less, hopefully much less 
if you have very long input strings.

I really don't know what set me off looking at this; it's just a little 
random experiment I suppose.

Thread

Patricia trie vs binary search. markspace <-@.> - 2012-05-24 16:07 -0700
  Re: Patricia trie vs binary search. glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-05-24 23:39 +0000
    Re: Patricia trie vs binary search. markspace <-@.> - 2012-05-24 17:56 -0700
      Password quality (Was: Patricia trie vs binary search.) Lew <lewbloch@gmail.com> - 2012-05-25 09:41 -0700
        Re: Password quality (Was: Patricia trie vs binary search.) markspace <-@.> - 2012-05-25 12:17 -0700
  Re: Patricia trie vs binary search. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-26 17:30 -0700
    Re: Patricia trie vs binary search. markspace <-@.> - 2012-05-26 18:17 -0700
    Re: Patricia trie vs binary search. Gene Wirchenko <genew@ocis.net> - 2012-05-27 18:44 -0700
      Re: Patricia trie vs binary search. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-27 22:00 -0700
        Re: Patricia trie vs binary search. markspace <-@.> - 2012-05-28 08:20 -0700
          Re: Patricia trie vs binary search. markspace <-@.> - 2012-05-28 14:38 -0700
        Re: Patricia trie vs binary search. Gene Wirchenko <genew@ocis.net> - 2012-05-28 09:20 -0700
          Re: Patricia trie vs binary search. Lew <noone@lewscanon.com> - 2012-05-28 21:54 -0700
            Re: Patricia trie vs binary search. Gene Wirchenko <genew@ocis.net> - 2012-05-29 09:14 -0700
              Re: Patricia trie vs binary search. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-29 09:55 -0700
                Re: Patricia trie vs binary search. Gene Wirchenko <genew@ocis.net> - 2012-05-29 11:17 -0700
                Re: Patricia trie vs binary search. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-29 11:22 -0700
                Re: Patricia trie vs binary search. Gene Wirchenko <genew@ocis.net> - 2012-05-29 14:44 -0700
                Re: Patricia trie vs binary search. Lew <lewbloch@gmail.com> - 2012-05-29 14:03 -0700
                Re: Patricia trie vs binary search. Gene Wirchenko <genew@ocis.net> - 2012-05-29 14:49 -0700
                Re: Patricia trie vs binary search. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-29 15:23 -0700
                Re: Patricia trie vs binary search. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-29 15:39 -0700
                Re: Patricia trie vs binary search. Gene Wirchenko <genew@ocis.net> - 2012-05-29 16:08 -0700
                Re: Patricia trie vs binary search. Lew <lewbloch@gmail.com> - 2012-05-29 18:25 -0700
            Re: Patricia trie vs binary search. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-29 09:16 -0700
              Re: Patricia trie vs binary search. Jeff Higgins <jeff@invalid.invalid> - 2012-05-29 13:37 -0400
                Re: Patricia trie vs binary search. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-29 10:49 -0700
                Re: Patricia trie vs binary search. Jeff Higgins <jeff@invalid.invalid> - 2012-05-29 13:58 -0400
                Re: Patricia trie vs binary search. Jeff Higgins <jeff@invalid.invalid> - 2012-05-29 14:20 -0400
                Re: Patricia trie vs binary search. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-05-29 11:21 -0700
                Re: Patricia trie vs binary search. Jeff Higgins <jeff@invalid.invalid> - 2012-05-29 14:29 -0400
                Re: Patricia trie vs binary search. Jeff Higgins <jeff@invalid.invalid> - 2012-05-29 15:00 -0400
  Re: Patricia trie vs binary search. Jeff Higgins <jeff@invalid.invalid> - 2012-05-29 09:24 -0400

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