Task — Word sorter

You are give a sentence. Write a script to order the words in the given sentence alphabetically but keeping the words themselves unchanged.

Examples

Example 1
Input: $str = 'The quick brown fox'
Output: 'brown fox quick The'

Example 2
Input: $str = 'Hello    World!   How   are you?'
Output: 'are Hello How World! you?'

Example 3
Input: $str = 'Hello'
Output: 'Hello'

Example 4
Input: $str = 'Hello, World! How are you?'
Output: 'are Hello, How World! you?'

Example 5
Input: $str = 'I have 2 apples and 3 bananas!'
Output: '2 3 and apples bananas! have I'

Analysis

The principle behind my solution is to split the sentence into words and then create a hash like this:

$words{lc($word)} = $word;

I can then sort keys %words and output $words{$key}, ie sort the words on their lower-cased version and output the original version.

But that doesn't work if there's a repeated word, as the second occurrence will overwrite the first in the hash. To avoid that, I append a unique number to the hash key, like this:

$words{lc($1) . ++ $i} = $1

So if the sentence is 'two cats, two dogs' the hash keys will be 'two1', 'cats2', 'two3', 'dogs4'.

As always, I tested it with the edge cases of no words and just one word.

Try it 

#!/usr/bin/perl

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

use v5.26;    # The Weekly Challenge - 2026-02-09
use utf8;     # Week 360 - task 2 - Word sorter
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';
use Encode;

word_sorter('The quick brown fox');
word_sorter('Hello    World!   How   are you?');
word_sorter('Hello');
word_sorter('I have 2 apples and 3 bananas!');
word_sorter('one two three, one two three');
word_sorter('');
word_sorter('justoneword');

sub word_sorter {
    
    my ($sentence, %words, $key, $output, $i);
    
    # initialise
    $sentence = $_[0];
    
    # make eg $words{fred} = 'Fred'
    $words{lc($1) . ++ $i} = $1 while $sentence =~ m|([^\s]+)|g;
    
    # sort by key and concatenate values
    $output = '';
    for $key (sort{$a cmp $b} keys %words) {
        $output .= $words{$key} . ' ';
    }
    
    say qq[\nInput:  '$sentence'];
    say qq[Output: '] . substr($output, 0, -1) . q['];
}

Output

Input:  'The quick brown fox'
Output: 'brown fox quick The'

Input:  'Hello    World!   How   are you?'
Output: 'are Hello How World! you?'

Input:  'Hello'
Output: 'Hello'

Input:  'I have 2 apples and 3 bananas!'
Output: '2 3 and apples bananas! have I'

Input:  'one two three, one two three'
Output: 'one one three, three two two'

Input:  ''
Output: ''

Input:  'justoneword'
Output: 'justoneword'