3Re: Help on array element counting

The idea is to loop through the original array. For each element, either look up or add that element as a key into a hash, and increments that key's value by one. Since Perl's hashes use autovivification, when we try to look up a non-existing key in a hash, that key will be added.

$hash{$_}++ for @array;
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is a very common Perl idiom. If we are processing the element 'APPLE' and it is not in the hash, a new key will be added to the hash, and that key's value (currently undef) will be incremented by 1 ... yielding 1. Later, if we encounter 'APPLE' again, when we try to look up 'APPLE' it exists this time and the value returned is 1. Add 1 to that and now we have 2 apples.

Remember, Data::Dumper is your friend! Try this out:

use strict;
use warnings;
use Data::Dumper;

my @fruit = qw(
      MANGO APPLE GRAPES MANGO MANGO MANGO
      MANGO APPLES APPLES BANANA CORN APPLES
);

my %fruit;
$fruit{$_}++ for @fruit;

print Dumper \@fruit;
print Dumper \%fruit;
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jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

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