The weekly challenge 337 - Task 1: Smaller Than Current

 1 #!/usr/bin/env perl
 2 # https://theweeklychallenge.org/blog/perl-weekly-challenge-337/#TASK1
 3 #
 4 # Task 1: Smaller Than Current
 5 # ============================
 6 #
 7 # You are given an array of numbers, @num1.
 8 #
 9 # Write a script to return an array, @num2, where $num2[i] is the count of all
10 # numbers less than or equal to $num1[i].
11 #
12 ## Example 1
13 ##
14 ## Input: @num1 = (6, 5, 4, 8)
15 ## Output: (2, 1, 0, 3)
16 ##
17 ## index 0: numbers <= 6 are 5, 4    => 2
18 ## index 1: numbers <= 5 are 4       => 1
19 ## index 2: numbers <= 4, none       => 0
20 ## index 3: numbers <= 8 are 6, 5, 4 => 3
21 #
22 #
23 ## Example 2
24 ##
25 ## Input: @num1 = (7, 7, 7, 7)
26 ## Output: (3, 3, 3, 3)
27 #
28 #
29 ## Example 3
30 ##
31 ## Input: @num1 = (5, 4, 3, 2, 1)
32 ## Output: (4, 3, 2, 1, 0)
33 #
34 #
35 ## Example 4
36 ##
37 ## Input: @num1 = (-1, 0, 3, -2, 1)
38 ## Output: (1, 2, 4, 0, 3)
39 #
40 #
41 ## Example 5
42 ##
43 ## Input: @num1 = (0, 1, 1, 2, 0)
44 ## Output: (1, 3, 3, 4, 1)
45 #
46 ############################################################
47 ##
48 ## discussion
49 ##
50 ############################################################
51 #
52 # First, we generate a descendingly sorted copy of @num1. Then, for
53 # each element of @num1, we search for the first element inside
54 # the sorted copy that is equal to the current number. From there we can
55 # calculate the number of elements that are less than or equal to the
56 # number by substracting the current index from the index of the last
57 # element in the sorted list.
58 
59 use v5.36;
60 use Data::Dumper;
61 
62 smaller_than_current(6, 5, 4, 8);
63 smaller_than_current(7, 7, 7, 7);
64 smaller_than_current(5, 4, 3, 2, 1);
65 smaller_than_current(-1, 0, 3, -2, 1);
66 smaller_than_current(0, 1, 1, 2, 0);
67 
68 sub smaller_than_current( @num1 ) {
69     say "Input: (" . join(", ", @num1) . ")";
70     my @numsorted = sort { $b <=> $a } @num1;
71     my @num2 = ();
72     foreach my $n (@num1) {
73         foreach my $i (0..$#numsorted) {
74             if($n == $numsorted[$i]) {
75                 push @num2, $#numsorted-$i;
76                 last;
77             }
78         }
79     }
80 
81     say "Output: (" . join(", ", @num2) . ")";
82 }
83