Task — String alike

You are given a string of even length. Write a script to find out whether the given string can be split into two halves of equal lengths, each with the same non-zero number of vowels.

Examples

Example 1
Input: $str = 'textbook'
Output: false
1st half: 'text' (1 vowel)
2nd half: 'book' (2 vowels)

Example 2
Input: $str = 'book'
Output: true
1st half: 'bo' (1 vowel)
2nd half: 'ok' (1 vowel)

Example 3
Input: $str = 'AbCdEfGh'
Output: true
1st half: 'AbCd' (1 vowel)
2nd half: 'EfGh' (1 vowel)

Example 4
Input: $str = 'rhythmmyth'
Output: false
1st half: 'rhyth' (0 vowel)
2nd half: 'mmyth' (0 vowel)

Example 5
Input: $str = 'UmpireeAudio'
Output: false
1st half: 'Umpire' (3 vowels)
2nd half: 'eAudio' (5 vowels)

Analysis

This challenge can be solved many different ways, and I tried several before choosing the one to submit.

I began writing software when computers were many orders of magnitude slower than they are today, and I retain a desire to write software which is efficient, as well as being correct, maintainable and robust.

So my solution is efficient in that it makes a single pass along the string. Although substr($string, $c, 1) looks messy, experience shows that Perl handles that very efficiently.

On the other hand, $x =~ m|[aeiou]|i is not the fastest way of identifying a vowel, though it is easy to understand. I think, though haven't tested it, that

$x eq 'a' or $x eq 'e' or $x eq 'i' 
   or $x eq 'o' or $x eq 'u'

would be faster - having first lower-cased the string.

Another option is to start by chopping the string in two and counting the vowels in each half separately. That makes for more code, but avoids the messing around with $h in my code.

So lots of options and I will read the other submissions with interest.

Try it 

#!/usr/bin/perl

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

use v5.26;    # The Weekly Challenge - 2025-11-17
use utf8;     # Week 348 - task 1 - String alike
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';
use Encode;

string_alike('rhythm');
string_alike('artifice');
string_alike('MOONSOUP');
string_alike('fairzzzz');
string_alike('uu');
string_alike('aeioupaeioupaeiuopaeioupaeioupaeiuop');
string_alike('123+!£ a $#FF & U (]');

sub string_alike {
    
    my ($string, $output, $size, $half, @count, $c, $h);
    
    # initialise
    $string = $_[0];
    $output = 'false';
    @count = (0, 0);

    # check for even length
    $size = length($string);
    if (($size & 1) == 0) {
        $half = $size / 2;
        $h = 0;
        
        # count vowels
        for $c (0 .. $size - 1) {       
            $h = 1 if $c == $half;
            $count[$h] ++ if substr($string, $c, 1) =~ m|[aeiou]|i;
        }
        
        # check for equality
        if ($count[0] != 0 and $count[0] eq $count[1]) {
            $output = qq[true - $count[0] vowel] . ($count[0] == 1 ? '' : 's');
        }
    }
    
    say qq[\nInput:  '$string'];
    say qq[Output: $output];
}

Output

Input:  'rhythm'
Output: false

Input:  'artifice'
Output: true - 2 vowels

Input:  'MOONSOUP'
Output: true - 2 vowels

Input:  'fairzzzz'
Output: false

Input:  'uu'
Output: true - 1 vowel

Input:  'aeioupaeioupaeiuopaeioupaeioupaeiuop'
Output: true - 15 vowels