Task — Equal group

You are given an array of integers. Write a script to return true if the given array can be divided into one or more groups: each group must be of the same size as the others, with at least two members, and with all members having the same value.

From example 3 we can see that if several group sizes are possible, we are to return the largest.

Examples

Example 1
Input: @ints = (1,1,2,2,2,2)
Output: true
Groups: (1,1), (2,2), (2,2)

Example 2
Input: @ints = (1,1,1,2,2,2,3,3)
Output: false
Groups: (1,1,1), (2,2,2), (3,3)

Example 3
Input: @ints = (5,5,5,5,5,5,7,7,7,7,7,7)
Output: true
Groups: (5,5,5,5,5,5), (7,7,7,7,7,7)

Example 4
Input: @ints = (1,2,3,4)
Output: false

Example 5
Input: @ints = (8,8,9,9,10,10,11,11)
Output: true
Groups: (8,8), (9,9), (10,10), (11,11)

Analysis

I have solved this in a straightforward way:

• Loop down over possible group sizes - ie integer submultiples of the array size, and
• check to see if all the members of each group are identical.

And that's it.

Try it 

Try running the script with any input:

Your @array =

example: 5, 5, 5, 9, 9, 9, 0, 0, 0

⤡

#!/usr/bin/perl

# Blog: http://ccgi.campbellsmiths.force9.co.uk/challenge

use v5.26;    # The Weekly Challenge - 2025-08-25
use utf8;     # Week 336 - task 1 - Equal group
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';
use Encode;

equal_group(1, 1, 2, 2, 2, 2);
equal_group(1, 1, 1, 2, 2, 2, 3, 3);
equal_group(5, 5, 5, 5, 5, 5, 7, 7, 7, 7, 7, 7);
equal_group();
equal_group(42);
equal_group(77, 77);
equal_group(-1, -1, -1, -1, -1, -1, -1, -1, -1, -1);

sub equal_group {
    
    my (@array, $result, $size, $groups, $group, $start, $member, $output);
    
    # initialise
    @array = @_;
    $result = 'false';
    
    # loop down over possible group sizes
    SIZE: for ($size = scalar @array; $size >= 2; $size --) {
        
        # check for integral number of groups
        $groups = scalar @array / $size;
        next SIZE unless $groups == int($groups);
        
        # check each group
        $output = '(';
        for $group (0 .. $groups - 1) {
            $start = $group * $size;
            
            # check each member
            for $member (0 .. $size - 1) {
                next SIZE unless $array[$start + $member] == $array[$start];
                $output .= qq[$array[$start + $member], ];
            }
            $output = substr($output, 0, -2) . '), (';
        }
        $result = qq[true - ] . substr($output, 0, -3);
        last;
    }
    
    say qq[\nInput:  (] . join(', ', @array) . ')';
    say qq[Output: $result];
}

Output

Input:  (1, 1, 2, 2, 2, 2)
Output: true - (1, 1), (2, 2), (2, 2)

Input:  (1, 1, 1, 2, 2, 2, 3, 3)
Output: false

Input:  (5, 5, 5, 5, 5, 5, 7, 7, 7, 7, 7, 7)
Output: true - (5, 5, 5, 5, 5, 5), (7, 7, 7, 7, 7, 7)

Input:  ()
Output: false

Input:  (42)
Output: false

Input:  (77, 77)
Output: true - (77, 77)

Input:  (-1, -1, -1, -1, -1, -1, -1, -1, -1, -1)
Output: true - (-1, -1, -1, -1, -1, -1, -1, -1, -1, -1)