The weekly challenge 327 - Task 2: MAD

 1 #!/usr/bin/env perl
 2 # https://theweeklychallenge.org/blog/perl-weekly-challenge-327/#TASK2
 3 #
 4 # Task 2: MAD
 5 # ===========
 6 #
 7 # You are given an array of distinct integers.
 8 #
 9 # Write a script to find all pairs of elements with minimum absolute difference
10 # (MAD) of any two elements.
11 #
12 ## Example 1
13 ##
14 ## Input: @ints = (4, 1, 2, 3)
15 ## Output: [1,2], [2,3], [3,4]
16 ##
17 ## The minimum absolute difference is 1.
18 ## Pairs with MAD: [1,2], [2,3], [3,4]
19 #
20 #
21 ## Example 2
22 ##
23 ## Input: @ints = (1, 3, 7, 11, 15)
24 ## Output: [1,3]
25 #
26 #
27 ## Example 3
28 ##
29 ## Input: @ints = (1, 5, 3, 8)
30 ## Output: [1,3], [3,5]
31 #
32 ############################################################
33 ##
34 ## discussion
35 ##
36 ############################################################
37 #
38 # We take two walks of the array. First, we find the MAD by calculating
39 # all absolute distances, keeping track of the minimum. Then, we keep all
40 # pairs of numbers where the absolute distance matches the minimum. For
41 # a nicer output, we sort the pairs that we keep by size, and in the end
42 # we sort the output by size as well.
43 
44 use v5.36;
45 
46 mad(4, 1, 2, 3);
47 mad(1, 3, 7, 11, 15);
48 mad(1, 5, 3, 8);
49 
50 sub mad(@ints) {
51     say "Input: (" . join(", ", @ints) . ")";
52     my $mad = abs($ints[0] - $ints[1]);
53     my @output = ();
54     foreach my $i (0..$#ints) {
55         foreach my $j ($i+1..$#ints) {
56             my $ad = abs($ints[$i] - $ints[$j]);
57             $mad = $ad if $mad > $ad;
58         }
59     }
60     foreach my $i (0..$#ints) {
61         foreach my $j ($i+1..$#ints) {
62             my $ad = abs($ints[$i] - $ints[$j]);
63             if($ad == $mad) {
64                 push @output, $ints[$i] > $ints[$j] ? [$ints[$j], $ints[$i]] : [$ints[$i], $ints[$j]];
65             }
66         }
67     }
68     say "Output: " . join(", ", map { "[$_->[0], $_->[1]]" } sort { $a->[0] <=> $b->[0] } @output);
69 }