Beefy Boxes and Bandwidth Generously Provided by pair Networks
P is for Practical
 
PerlMonks  

Re: (Golf) Dependency List Prioritization

by AidanLee (Chaplain)
on Mar 14, 2002 at 18:32 UTC ( #151777=note: print w/replies, xml ) Need Help??


in reply to (Golf) Dependency List Prioritization

Thanks for making such an accessible golf problem (at least it feels so to me). here's 116 (my first golf):

sub f{my%h=@_;for(values %h){for(@$_){$h{$_}=[]if!$h{$_}}} print join(', ',sort{(grep /^$b$/,@{$h{$a}})?1:-1}keys%h)}
update: cool, i can rip some stuff out if i assume the test harness that tadman provided. 97:
sub f{%h=@_;for(values %h){for(@$_){$h{$_}=[]if!$h{$_}}} sort{(grep /^$b$/,@{$h{$a}})?1:-1}keys%h}

Replies are listed 'Best First'.
Re: Re: (Golf) Dependency List Prioritization
by AidanLee (Chaplain) on Mar 15, 2002 at 14:16 UTC

    I think i'm getting the hang of this. Here's 90:

    sub f{%h=@_;for(values %h){for(@$_){$h{$_}||=[]}} sort{(grep /^$b$/,@{$h{$a}})?1:-1}keys%h}
      Nice idea.

      A few minor nits though. First is that it is customary to only count the body of the sub, so you actually did slightly better than you thought! A second minor issue is that your grep is not quite right - the string "fooey\n" will match /^fooey$/ so you don't really have an equality test.

      Further than that, there are some mechanical tricks that can be used to improve scores. Such as using an inline for loop, using map to avoid double loops, and the like. Using those I can take your answer to 75 fairly easily:

      sub f{ #23456789_123456789_123456789_123456789_123456789_123456789_123456789_ +12345 %h=@_;$h{$_}||=[]for map@$_,values%h;sort{-1+2*grep$_ eq$b,@{$h{$a}}}k +eys%h }

      UPDATE
      Oops. I didn't notice the lack of transitivity in your code. This is a fatal flaw as you see with the following data set.

      my @list = ( a => ['b'], b => ['c'], c => ['d'], d => ['e'], );

      Assuming the test harness provided, I doubt anyone can beat this:

      sub f{d,c,b,a,f,e}

      Try this for a test harness:

      my @list = ( a => [ 'b', 'c', 'e' ], b => [ 'd' ], c => [ 'b', 'd' ], f => [ 'a' ], ); print join (',', map { "'$_'" } f(@list)),"\n";

      Your code produces 'd','b','c','f','e','a', which does not reflect the fact that 'f' depends on 'a'.

      So, I am afraid your solution holds only for a limited set of test harnesses -- and is certainly not the shortest among such solutions.

      The Sidhekin
      print "Just another Perl ${\(trickster and hacker)},"

      I hope you don't mind me removing a few bytes:

      sub f{for(values(%h=@_)){$h{$_}||=[]for@$_}sort{(grep/^$b$/,@{$h{$a}}) +||-1}keys%h}
      (Note: I didn't test)

      U28geW91IGNhbiBhbGwgcm90MTMgY
      W5kIHBhY2soKS4gQnV0IGRvIHlvdS
      ByZWNvZ25pc2UgQmFzZTY0IHdoZW4
      geW91IHNlZSBpdD8gIC0tIEp1ZXJk
      

        If you test, you will find it doesn't compile.

Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Node Status?
node history
Node Type: note [id://151777]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others exploiting the Monastery: (2)
As of 2022-05-22 23:39 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    Do you prefer to work remotely?



    Results (81 votes). Check out past polls.

    Notices?