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Code Shortening (golf) [RESOLVED]

by Young Monk (Novice)
on Oct 18, 2010 at 18:41 UTC ( #866017=perlquestion: print w/replies, xml ) Need Help??
Young Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi all. I was trying a question in SPOJ. Let me explain the question first. The input will be a single line containing capital and small letters. Lets assume the following:
Capital Letters-Opcode
Small Letters-Operands
In AbcdEf,
A is an opcode. The operands of A are b,c and d. Similarly, E is an opcode and its operands are f. The opcodes must be moved to the closest upper index that is a multiple of 4.

So, AbcD must be Abc-D, where '-' means a blank (output is 1).
Similarly, ABC must be A---B---C, so the output is 6.
Similarly, AbcdeF must be Abcde---F, so the output is 3.
The task is, to find the minimum number of '-'s that are needed to be inserted to align the Opcodes accordingly.

Here is my solution to this task:
It is 42 chars long and its the second shortest. The first shortest is 39 chars long. Can u pls try to make it shorter?

Edit2: Corrected a small typo. (thanks to Ken)

Replies are listed 'Best First'.
Re: Code Shortening (golf)
by eyepopslikeamosquito (Chancellor) on Oct 18, 2010 at 20:55 UTC

    My general golfing advice is to try to use $\ as the accumulator if you possibly can because you can then print it with a bald print.

    For example, this one is six strokes shorter and gives the same result as yours for the three test cases given at the spoj web site:

    Don't know if it's generally valid though.

      It will fail for a test case like AB for which, it must be A---B, (ie) output is 3.
      In my solution, decrementing 3 from the result is necessary. So, a bald 'print' cant be used! Any suggestions?

        So, a bald 'print' cant be used!
        To be a competitive golfer you have to be tenacious, devious and challenge assumptions. So I wouldn't rule out using a bald print just yet. At least, not without first trying to find a way to adjust your algorithm so that it can be used.

        For example, why do you subtract 3 at the end, as in print$n-3? Is that to compensate for adding 3 when you (always) match at start of string? If so, you could try to eliminate the need to subtract 3 by adjusting your regex to not match at start of string.

        In any case, I suggest you study every line of perlre looking for something, anything, that might help you shave a stroke. That is the attitude required to win at golf.

Re: Code Shortening (golf)
by moritz (Cardinal) on Oct 18, 2010 at 19:43 UTC
    If you're allowed to use command line options like -n and -E:
    $ echo EaEbFabG | perl -nE'$n+=~y///c&3for/(.*?)[A-Z]/g;say$n-3' 5
    Perl 6 - links to (nearly) everything that is Perl 6.
Re: Code Shortening (golf)
by toolic (Bishop) on Oct 18, 2010 at 18:54 UTC
    Save 2 by changing print to say.

    A link to whatever site you're looking at would be handy.

      But for using "say", we must include a line before the script like "use 5.10" rite? (not quite sure about the version)
        If you write a one-liner, using -E instead of -e enables the new features like say.
        Perl 6 - links to (nearly) everything that is Perl 6.
Re: Code Shortening (golf)
by kcott (Canon) on Oct 18, 2010 at 19:57 UTC
    Similarly, AbcdeF must be Abcde(NOP)(NOP)F, so the output is 2.

    Shouldn't that be: Similarly, AbcdeF must be Abcde(NOP)(NOP)(NOP)F, so the output is 3.

    Using hyphens instead of (NOP)s:


    It may just be a typo. If not, I haven't understood the task.

    -- Ken

Re: Code Shortening (golf)
by aquarium (Curate) on Oct 19, 2010 at 22:42 UTC
    i like this puzzle/question.
    how about just looking up the position of each capital letter (discounting first one), to see that the position aligns with modulus 4. totally untested proof of concept code below
    $n+=4-len($`)%4 for(/[A-Z]/g);print $n-4;
    maybe wiser monks (with access to perl) could try or comment.
    the hardest line to type correctly is: stty erase ^H
      Actually, my solution is similar to yours. The elongated solution is:
      $n+=3-length($_)%4 for<>=~/(.*?)[A-Z]/g;print$n-3

      Lately, I found out about the bit-wise operator '&' and substituted it.

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