|Perl: the Markov chain saw|
Comparison by position and valueby BrowserUk (Pope)
|on Jan 02, 2005 at 09:32 UTC||Need Help??|
BrowserUk has asked for the
wisdom of the Perl Monks concerning the following question:
Given two strings of equal length that contain digits and some placeholder value, I want a fast way to determine if the pair are 'compatible'.
Eg. Given (where underscore represents the placeholder but this could be substituted by any other non-digit value that helped the algorithm)
These two strings are compatible because no single digit appears in both strings except where it appears in the same position (8)
Whereas these two would be incompatible
because the digit 8 appears in both, but at a different position. And these two are incompatible
because the second last digit in both strings contains a different value.
I know how to do this with a loop and substr and a hash, but it is rather slow and I have a set N of M sets of these strings and I want to produce a set P, where each element of P is a string that is combines one string from as many of the N sets of strings as are compatible. Given the combinatorial nature of the problem, I need to make it as quick as possible.
I keep thinking that this can be done using string-wise boolean operations, but I cannot see how?
If there is a better way of structuring the data (eg. arrays of char rather than strings) that makes the process quicker or easier that's good to.
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