Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl: the Markov chain saw
 
PerlMonks  

Re: Problems with looping through an array

by gmax (Abbot)
on May 27, 2004 at 10:34 UTC ( #356855=note: print w/ replies, xml ) Need Help??


in reply to Problems with looping through an array

Use a hash to get a count of each unique item.

#!/usr/bin/perl -w use strict; use Data::Dumper; my @ID = (1,1,1,1,1,1,1,1,2,2,2,2,2,2,3,3,4,4,4,4,4,5,5,5,5); # # count # my %items =(); $items{$_}++ for @ID; print "$_ => $items{$_}\n" for sort keys %items; # # detail # %items =(); my $count =0; push @{$items{$_}}, $count++ for @ID; print Data::Dumper->Dump([ \%items], ['items']); __END__ output: 1 => 8 2 => 6 3 => 2 4 => 5 5 => 4 $items = { '4' => [ 16, 17, 18, 19, 20 ], '1' => [ 0, 1, 2, 3, 4, 5, 6, 7 ], '3' => [ 14, 15 ], '2' => [ 8, 9, 10, 11, 12, 13 ], '5' => [ 21, 22, 23, 24 ] };

(update) Instead of Data::Dumper, you could also get your details this way:

print "$_ => (@{$items{$_}})\n" for sort keys %items ; __END__ 1 => (0 1 2 3 4 5 6 7) 2 => (8 9 10 11 12 13) 3 => (14 15) 4 => (16 17 18 19 20) 5 => (21 22 23 24)

See also Perl Idioms Explained - keys %{{map{$_=>1}@list}} in Tutorials to see how the hash mechanism works.

As for the error in your code, this node could be of help.

 _  _ _  _  
(_|| | |(_|><
 _|   


Comment on Re: Problems with looping through an array
Select or Download Code

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://356855]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others browsing the Monastery: (12)
As of 2015-07-06 15:42 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (77 votes), past polls