Robbie Hatley's Solutions, in Perl, for The Weekly Challenge #310 ("Arrays Intersection" and "Sort Odd Even")

For those not familiar with "The Weekly Challenge", it is a weekly programming puzzle with two parts, cycling every Sunday. You can find it here:

The Weekly Challenge

The Weekly Challenge for the week of 2025-02-24 through 2025-03-02 is #310.

The tasks for challenge #310 are as follows:

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Task 310-1: Arrays Intersection
Submitted by: Mohammad Sajid Anwar
You are given a list of arrays of integers. Write a script to
return the common elements in all the arrays.

Example #1:
Input: $list = ( [1, 2, 3, 4], [4, 5, 6, 1], [4, 2, 1, 3] )
Output: (1, 4)

Example #2:
Input: $list = ( [1, 0, 2, 3], [2, 4, 5] )
Output: (2)

Example #3:
Input: $list = ( [1, 2, 3], [4, 5], [6] )
Output: ()

I'll start by writing a subroutine that determines whether a given integer is in a given array of integers. Then I'll write a sub that determines whether a given integer is in all of the given arrays. Finally, I'll write a sub that determines the common elements between multiple arrays.

Robbie Hatley's Perl Solution to The Weekly Challenge 310-1

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Task 310-2: Sort Odd Even
Submitted by: Mohammad Sajid Anwar
You are given an array of integers. Write a script to sort odd
index elements in decreasing order and even index elements in
increasing order in the given array.

Example #1:
Input: @ints = (4, 1, 2, 3)
Output: (2, 3, 4, 1)
Even index elements: 4, 2 => 2, 4 (increasing order)
Odd index elements : 1, 3 => 3, 1 (decreasing order)

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

Example #3:
Input: @ints = (5, 3, 2, 1, 4)
Output: (2, 3, 4, 1, 5)
Even index elements: 5, 2, 4 => 2, 4, 5 (increasing order)
Odd index elements : 3, 1 => 3, 1 (decreasing order)

I'll first separate the odd and even elements into to separate arrays, sort them separately (odds decending, evens ascending), then use the "mesh" function from CPAN module "List::SomeUtils" to mesh them together.

Robbie Hatley's Perl Solution to The Weekly Challenge 310-2

That's it for challenge 310; see you on challenge 311!