Advent Calendar 2023

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The gift is presented by Ian Rifkin. Today he is talking about his solution to The Weekly Challenge - 240. This is re-produced for Advent Calendar 2023 from the original post.

A.A.B.A. (Acronym And Build Array)

Task 1: Acronym

You are given an array of strings and a check string.
Write a script to find out if the check string is the acronym of the words in the given array.

Example 1

    Input: @str = ("Perl", "Python", "Pascal")
           $chk = "ppp"
       Output: true

Example 2

       Input: @str = ("Perl", "Raku")
           $chk = "rp"
         Output: false

Example 3

    Input: @str = ("Oracle", "Awk", "C")
           $chk = "oac"
    Output: true

I am sure there are plenty of more interesting ways to solve this but the way my mind works is to create a real acronym by looping through each word in the in the input array to get the first letter.

sub check_acronym {
    my ($acronym, $words) = @_;
    my $real_acronym;
    foreach (@{$words}) {
        $real_acronym .= substr($_, 0, 1);
    }

With that in place just compare the strings, forcing them both into uppercase so that it’s a case insensitive comparison. You could also do this with a simple RegEx compare but this feels simpler to write/read to my brain.

uc($acronym) eq uc($real_acronym) ? print "true\n" : print "false\n";

I did a similar approach with Raku and Python. With Perl the final print statement is a conditional so that it will print the words "true" or "false" instead of 0 or 1 but that’s not needed with Python and Raku.

Source Code

[   Perl   |   Raku   |   Python   ]

Task 2: Build Array

You are given an array of integers.
Write a script to create an array such that new[i] = old[old[i]] where 0 <= i < new.length.

Example 1
    Input: @int = (0, 2, 1, 5, 3, 4)
    Output: (0, 1, 2, 4, 5, 3)

Example 2
    Input: @int = (5, 0, 1, 2, 3, 4)
    Output: (4, 5, 0, 1, 2, 3)

Doing new[i] = old[old[i]] seemed simple enough but I do have trouble mentally processing where 0 <= i < new.length. If i is a postion of the input array it is always going to be equal to or greater than 0 because of how arrays are numbered. Since each new[i] is mapped to a value calculated from the old array they should naturally end up the same length, so i should never be longer than new.length because i shouldn’t be less than old.length either.

With that out of the way, I did a simple for loop using the iterator variable $i – within the loop I am literally just doing the exact mapping from the question: new[i] = old[old[i]]

for (my $i = 0; $i < @ints; $i++) {
    $new_ints[$i] = $ints[$ints[$i]];
}

That’s it! After the loop I print the new array in the desired format:

print "(" . join(', ', @new_ints) . ")\n";

This task sounded more complicated so I will be curious to see if others took a more interesting approach.

Source Code

[   Perl   |   Raku   |   Python   ]

If you have any suggestion then please do share with us perlweeklychallenge@yahoo.com.

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