The weekly challenge 326 - Task 2: Decompressed List

 1 #!/usr/bin/env perl
 2 # https://theweeklychallenge.org/blog/perl-weekly-challenge-326/#TASK2
 3 #
 4 # Task 2: Decompressed List
 5 # =========================
 6 #
 7 # You are given an array of positive integers having even elements.
 8 #
 9 # Write a script to to return the decompress list. To decompress, pick adjacent
10 # pair (i, j) and replace it with j, i times.
11 #
12 ## Example 1
13 ##
14 ## Input: @ints = (1, 3, 2, 4)
15 ## Output: (3, 4, 4)
16 ##
17 ## Pair 1: (1, 3) => 3 one time  => (3)
18 ## Pair 2: (2, 4) => 4 two times => (4, 4)
19 #
20 #
21 ## Example 2
22 ##
23 ## Input: @ints = (1, 1, 2, 2)
24 ## Output: (1, 2, 2)
25 ##
26 ## Pair 1: (1, 1) => 1 one time  => (1)
27 ## Pair 2: (2, 2) => 2 two times => (2, 2)
28 #
29 #
30 ## Example 3
31 ##
32 ## Input: @ints = (3, 1, 3, 2)
33 ## Output: (1, 1, 1, 2, 2, 2)
34 ##
35 ## Pair 1: (3, 1) => 1 three times => (1, 1, 1)
36 ## Pair 2: (3, 2) => 2 three times => (2, 2, 2)
37 #
38 ############################################################
39 ##
40 ## discussion
41 ##
42 ############################################################
43 #
44 # Since perl v5.36 has the possibility to run foreach with two elements
45 # of a list at once, we use that neat feature to walk all pairs of
46 # $i and $j. Then we put $j into the result $i times.
47 
48 use v5.36;
49 decompressed_list(1, 3, 2, 4);
50 decompressed_list(1, 1, 2, 2);
51 decompressed_list(3, 1, 3, 2);
52 
53 sub decompressed_list( @ints ) {
54     say "Input: (" . join(", ", @ints) . ")";
55     my @output = ();
56     foreach my ($i, $j) (@ints) {
57         foreach my $k (1..$i) {
58             push @output, $j;
59         }
60     }
61     say "Output: (" . join(", ", @output) . ")";
62 }