The weekly challenge 398 - Task 1: Divisible Average

 1 #!/usr/bin/env perl
 2 # https://theweeklychallenge.org/blog/perl-weekly-challenge-398/#TASK1
 3 #
 4 # Task 1: Divisible Average
 5 # =========================
 6 #
 7 # You are given an array of positive integers.
 8 #
 9 # Write a script to return the closest integer to the mean value of all even
10 # integers that are divisible by 3. If none is divisible, return 0.
11 #
12 ## Example 1
13 ##
14 ## Input: @arr = (18, 5, 7, 11)
15 ## Output: 18
16 ##
17 ## 18 is the only even number and divisible by 3.
18 ## Average: 18 / 1 = 18.
19 #
20 ## Example 2
21 ##
22 ## Input: @arr = (6, 12, 18, 24, 30, 40)
23 ## Output: 18
24 ##
25 ## The qualifying numbers are 6, 12, 18, 24, and 30.
26 ## Average: (6 + 12 + 18 + 24 + 30) / 5 = 90 / 5 = 18
27 #
28 ## Example 3
29 ##
30 ## Input: @arr = (3, 9, 15, 21, 27)
31 ## Output: 0
32 ##
33 ## None of the elements are even.
34 ## Since no elements qualify, return 0.
35 #
36 ## Example 4
37 ##
38 ## Input: @arr = (6, 12, 14, 20)
39 ## Output: 9
40 ##
41 ## The qualifying numbers are 6 and 12.
42 ## Average: (6 + 12) / 2 = 9.
43 #
44 ## Example 5
45 ##
46 ## Input: @arr = (6, 6, 6, 12, 12)
47 ## Output: 8
48 ##
49 ## All five numbers are even and divisible by 3.
50 ## Average: (6 + 6 + 6 + 12 + 12) / 5 = 8.4 => 8
51 #
52 ############################################################
53 ##
54 ## discussion
55 ##
56 ############################################################
57 #
58 # First, we collect all even numbers that are divisible by 3,
59 # which are exactly all numbers divisible by 6. Then we calculate
60 # their average, add 0.5 and take the integer value of that.
61 #
62 use v5.36;
63 use List::Util qw(sum);
64 
65 sub divisible_average(@arr) {
66     say "Input: (" . join(", ", @arr) . ")";
67     my @divisible = grep { $_ % 6 == 0 } @arr;
68     return say "Output: 0" unless @divisible;
69     my $count = scalar(@divisible);
70     my $avg = int( sum(@divisible) / $count + 0.5);
71     say "Output: $avg";
72 }
73 
74 
75 divisible_average(18, 5, 7, 11);
76 divisible_average(6, 12, 18, 24, 30, 40);
77 divisible_average(3, 9, 15, 21, 27);
78 divisible_average(6, 12, 14, 20);
79 divisible_average(6, 6, 6, 12, 12);