## Perl Weekly Challenge 276: Maximum Frequency

These are some answers to the Week 276, Task 2, of the Perl Weekly Challenge organized by Mohammad S. Anwar.

*Spoiler Alert:* This weekly challenge deadline is due in a few days from now (on July 7, 2024 at 23:59). This blog post provides some solutions to this challenge. Please don’t read on if you intend to complete the challenge on your own.

## Task 2: Maximum Frequency

*You are given an array of positive integers, @ints.*

*Write a script to return the total number of elements in the given array which have the highest frequency.*

*Example 1*

```
Input: @ints = (1, 2, 2, 4, 1, 5)
Ouput: 4
The maximum frequency is 2.
The elements 1 and 2 has the maximum frequency.
```

*Example 2*

```
Input: @ints = (1, 2, 3, 4, 5)
Ouput: 5
The maximum frequency is 1.
The elements 1, 2, 3, 4 and 5 has the maximum frequency.
```

### Maximum Frequency in Raku

We use a Bag to store the frequencies. This is very simple because we just need to coerce the input array to a `Bag`

in order to compute the various frequencies. Then, we compute the maximum frequency and finally count the items whose frequency is equal to the maximum frequency.

```
sub max-frequency (@in) {
my $frequencies = @in.Bag;
my $max = $frequencies.values.max;
my $count = 0;
for $frequencies.keys -> $i {
$count += $max if $frequencies{$i} == $max;
}
return $count;
}
my @tests = (1, 2, 2, 4, 1, 5), (1, 2, 3, 4, 5);
for @tests -> @test {
printf "%-15s => ", "@test[]";
say max-frequency @test;
}
```

This program displays the following output:

```
$ raku ./max-frequency.raku
1 2 2 4 1 5 => 4
1 2 3 4 5 => 5
```

### Maximum Frequency in Perl

This is a port to Perl of the above Raku program. Perl having no `Bags`

, we use a hash instead, but we need an explicit `for`

loop to compute the frequencies and populate the `%frequencies`

hash. Similarly, we need a `for`

loop to compute the maximum frequency.

```
use strict;
use warnings;
use feature 'say';
sub max_frequency {
my %frequencies;
for my $i (@_) {
$frequencies{$i}++;
} `
my $max = 0;
for my $i (values %frequencies) {
$max = $i if $i > $max;
}
my $count = 0;
for my $i (keys %frequencies) {
$count += $max if $frequencies{$i} == $max;
}
return $count;
}
my @tests = ( [1, 2, 2, 4, 1, 5], [1, 2, 3, 4, 5]);
for my $test (@tests) {
printf "%-15s => ", "@$test";
say max_frequency @$test;
}
```

This program displays the following output:

```
$ perl ./max-frequency.pl
1 2 2 4 1 5 => 4
1 2 3 4 5 => 5
```

## Wrapping up

The next week Perl Weekly Challenge will start soon. If you want to participate in this challenge, please check https://perlweeklychallenge.org/ and make sure you answer the challenge before 23:59 BST (British summer time) on July 14, 2024. And, please, also spread the word about the Perl Weekly Challenge if you can.

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