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Re^2: The greedy change-making problem using regexes

by Anonymous Monk
on Mar 10, 2005 at 10:45 UTC ( #438204=note: print w/replies, xml ) Need Help??

in reply to Re: The greedy change-making problem using regexes
in thread The greedy change-making problem using regexes

No need for code blocks, and it works very fast as well (as you'd expect from a greedy algorithm).
my $dime = '(?:' . ('1' x 10) . ')'; my $halfdozen = '(?:' . ('1' x 6) . ')'; my $nickel = '(?:' . ('1' x 5) . ')'; my $cent = '(?:' . ('1' x 1) . ')'; sub greedy_change { my $change = shift; my ($c10, $c6, $c5, $c1) = ('1' x $change) =~ /^($dime*)($halfdozen*)($nickel*)($cent*)$/; return (length ($c10 || "") / 10, length ($c6 || "") / 6, length ($c5 || "") / 5, length ($c1 || "") / 1); }

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Re^3: The greedy change-making problem using regexes
by japhy (Canon) on Mar 10, 2005 at 12:32 UTC
    No, that doesn't work: it ends up using three coins (a dime and two pennies) for 12 cents, instead of two six-cent coins.
    Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
    How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart
      Which is the correct answer for the greedy algorithm. But see my posting elsewhere in this thread for a more general solution.

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[Corion]: Discipulus: You got pushed too much under water?
[Corion]: marto: Oooh - cinema... I guess that's something I could do with my godson and sibling and sister as well, but I guess that getting a six year old and two four year olds into one movie is a tough sell ;)
[marto]: busy weekend, no me time :P
[Corion]: marto: Yeah, that's somewhat implied :) I was on the phone with my godson yesterday (they birthday), but I haven't seen them for two weeks now (vacation), relaxing, but I somewhat miss them too ;)
[Discipulus]: me waterpolo? oh no! i'm a no sport; the tournment was for the elder son
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[Corion]: Discipulus: Ah, so he's the one getting almost drowned all the time - waterpolo certainly is no sport for me ;)

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