Duplicate zeros

You are given an array of integers. Write a script to duplicate each occurrence of zero, shifting the remaining elements to the right. The elements beyond the length of the original array are not written.

Examples

Example 1
Input: @ints = (1, 0, 2, 3, 0, 4, 5, 0)
Output: (1, 0, 0, 2, 3, 0, 0, 4)
Each zero is duplicated.
Elements beyond the original length (like 5 and last 0) 
   are discarded.

Example 2
Input: @ints = (1, 2, 3)
Output: (1, 2, 3)
No zeros exist, so the array remains unchanged.

Example 3
Input: @ints = (1, 2, 3, 0)
Output: (1, 2, 3, 0)

Example 4
Input: @ints = (0, 0, 1, 2)
Output: (0, 0, 0, 0)

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

Analysis

This one's a bit simpler.

Step 1 is to create a new array mapping each 0 to (0, 0) and just copying over any non-zero elements.

Step 2 is to output the first n elements of the new array, where n is the number of elements in the input array.

The implementations provide excellent examples of how to approach these challenges in Perl, balancing correctness, clarity, and practicality. The detailed output formatting in Task 1 is particularly noteworthy for making the solutions more informative and useful.

Try it 

#!/usr/bin/perl

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

use v5.26;    # The Weekly Challenge - 2025-08-04
use utf8;     # Week 333 - task 2 - Duplicate zeros
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';
use Encode;

duplicate_zeros(1, 0, 2, 3, 0, 4, 5, 0);
duplicate_zeros(1, 2, 3);
duplicate_zeros(1, 2, 3, 0);
duplicate_zeros(0, 0, 1, 2);
duplicate_zeros(1, 2, 0, 3, 4);

sub duplicate_zeros {
    
    # map each 0 to 0, 0
    my @output = map($_ == 0 ? (0, 0) : $_, @_);
    
    # output as many elements in @output as in the input array
    say qq[\nInput:  (] . join(', ', @_) . ')';
    say qq[Output: (] . join(', ', @output[0 .. $#_]) . ')';
}

4 lines of code

Output from script

Input:  (1, 0, 2, 3, 0, 4, 5, 0)
Output: (1, 0, 0, 2, 3, 0, 0, 4)

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

Input:  (1, 2, 3, 0)
Output: (1, 2, 3, 0)

Input:  (0, 0, 1, 2)
Output: (0, 0, 0, 0)

Input:  (1, 2, 0, 3, 4)
Output: (1, 2, 0, 0, 3)