Array Question

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks, I have a simple question but it's confusing me. I have an array with multiple names and some of them are the same. I need to count how many instances of each letter are in this array, can some one give a little help here? Results should be like:
red=3
blue=2
white=2
yellow=1
...
Thanks for the help!

#! /perl/bin/perl 

use strict;

my @letters = ("red","red","red","blue","white","yellow","blue","navy"
+,"navy","green","white","cars");

foreach my $i (sort(@letters)) {

print "$i\n";

}
[download]

Comment on Array Question Download Code

Replies are listed 'Best First'.
Re: Array Question by Roy Johnson (Monsignor) on Aug 19, 2005 at 14:30 UTC
Count using a hash: `my %count; ++$count{$_} for @letters;` [download] Caution: Contents may have been coded under pressure.	[reply] [d/l]
Re: Array Question by Transient (Hermit) on Aug 19, 2005 at 14:30 UTC
There are many examples already in the monastery, but here's one way: `#! /perl/bin/perl use Data::Dumper; use strict; my @letters = ("red","red","red","blue","white","yellow","blue","navy" +,"navy","green","white","cars"); my %count = (); $count{$_}++ for @letters; print Dumper( \%count );` [download]	[reply] [d/l]
Re: Array Question by Roger (Parson) on Aug 19, 2005 at 14:33 UTC
There are two problems here: 1) count the occurance of words 2) display the words and occurances in decending order. Try this... `my %count; for (@letters) { $count{$_}++; } for ( map { $_->[0] } sort { $b->[1] <=> $a->[1] } map { [ $_, $count{$_} ] } keys %count ) { print $_, "=>", $count{$_}, "\n"; }` [download]	[reply] [d/l]
Re^2: Array Question by ikegami (Patriarch) on Aug 19, 2005 at 14:44 UTC
Using Schwartzian Transform here is overkill, because hash lookups are very efficient. Simplification: `my @letters = qw( red red red blue white yellow blue navy navy green white cars ); my %count; $count{$_}++ foreach @letters; print("$_ => $count{$_}\n") foreach sort { $count{$b} <=> $count{$a} } keys %count;` [download] Output: `red => 3 blue => 2 white => 2 navy => 2 cars => 1 green => 1 yellow => 1` [download] Kudos for being the first to sort the results, though.	[reply] [d/l] [select]