Array form compute

You are given an array of integers, @ints and an integer, $x. Write a script to add $x to the integer in array form.

The array form of an integer is a digit-by-digit representation stored as an array, where the most significant digit is at the 0th index.

Examples

Example 1
Input: @ints = (1, 2, 3, 4), $x = 12
Output: (1, 2, 4, 6)

Example 2
Input: @ints = (2, 7, 4), $x = 181
Output: (4, 5, 5)

Example 3
Input: @ints = (9, 9, 9), $x = 1
Output: (1, 0, 0, 0)

Example 4
Input: @ints = (1, 0, 0, 0, 0), $x = 9999
Output: (1, 9, 9, 9, 9)

Example 5
Input: @ints = (0), $x = 1000
Output: (1, 0, 0, 0)

Analysis

My one-line solution is:

• use join to convert @ints to a number
• add $x
• use split to convert that to an array

@x is stated to be 'an integer', so we have to allow for it being 0 or negative, which my algorithm covers. However, we aren't told how to represent a negative number in array form so I have assumed that this is not allowed, ie this is invalid:

@ints = (1, 2, 3); $x = -124

There is also the possibility that @ints or the result of the addition represent a number larger than can be represented as a Perl integer. My code fails in that case, but the algorithm is still valid if translated into Math::BigInt notation.

In the great majority of real-world use cases, this solution accurately resolves the issue and is clear, practical and effective. It creates a sophisticated one-liner by utilizing Perl's advantages in handling strings and numbers. The fundamental requirement of the problem—converting between array and numerical representations—is clearly understood by Peter.

This review may cover either or both challenges for this week.

Try it 

Try running the script with any input:

Your $ints =

example: 1, 2, 3, 4, 5

Your $x =

example: 54321

⤡

#!/usr/bin/perl

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

use v5.26;    # The Weekly Challenge - 2025-10-20
use utf8;     # Week 344 - task 1 - Array form compute
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';
use Encode;

array_form_compute([1, 2, 3, 4], 12);
array_form_compute([2, 7, 4], 181);
array_form_compute([9, 9, 9], 1);
array_form_compute([0, 1, 2, 3, 4], -17);
array_form_compute([1, 2, 3, 4], -1000);
array_form_compute([1, 2, 3, 4], -1234);
array_form_compute([0], 12345);

sub array_form_compute {
    
    say qq[\nInput:  \@ints = (] . join(', ', 
        @{$_[0]}) . qq[), \$x = $_[1]];
        
    # do it
    say qq[Output: (] . 
        join(', ', split('', join('', @{$_[0]}) + $_[1]))
        . ')';
}

6 lines of code

Output from script

Input:  @ints = (1, 2, 3, 4), $x = 12
Output: (1, 2, 4, 6)

Input:  @ints = (2, 7, 4), $x = 181
Output: (4, 5, 5)

Input:  @ints = (9, 9, 9), $x = 1
Output: (1, 0, 0, 0)

Input:  @ints = (0, 1, 2, 3, 4), $x = -17
Output: (1, 2, 1, 7)

Input:  @ints = (1, 2, 3, 4), $x = -1000
Output: (2, 3, 4)

Input:  @ints = (1, 2, 3, 4), $x = -1234
Output: (0)

Input:  @ints = (0), $x = 12345
Output: (1, 2, 3, 4, 5)