The weekly challenge 368 - Task 2: Big and Little Omega

 1 #!/usr/bin/env perl
 2 # https://theweeklychallenge.org/blog/perl-weekly-challenge-368/#TASK2
 3 #
 4 # Task 2: Big and Little Omega
 5 # ============================
 6 #
 7 # You are given a positive integer $number and a mode flag $mode. If the mode
 8 # flag is zero, calculate little omega (the count of all distinct prime factors
 9 # of that number). If it is one, calculate big omega (the count of all prime
10 # factors including duplicates).
11 #
12 ## Example 1
13 ##
14 ## Input: $number = 100061
15 ##        $mode = 0
16 ## Output: 3
17 ##
18 ## Prime factors are 13, 43, 179. Count is 3.
19 #
20 ## Example 2
21 ##
22 ## Input: $number = 971088
23 ##        $mode = 0
24 ## Output: 3
25 ##
26 ## Prime factors are 2, 2, 2, 2, 3, 20231. Count of distinct numbers is 3.
27 #
28 ## Example 3
29 ##
30 ## Input: $number = 63640
31 ##        $mode = 1
32 ## Output: 6
33 ##
34 ## Prime factors are 2, 2, 2, 5, 37, 43. Count including duplicates is 6.
35 #
36 ## Example 4
37 ##
38 ## Input: $number = 988841
39 ##        $mode = 1
40 ## Output: 2
41 #
42 ## Example 5
43 ##
44 ## Input: $number = 211529
45 ##        $mode = 0
46 ## Output: 2
47 #
48 ############################################################
49 ##
50 ## discussion
51 ##
52 ############################################################
53 #
54 # First, we create the list of prime factors. Then, dependent on
55 # $mode, we either keep it as is or filter it through List::Util's
56 # uniq() to get the list of distinct prime factors. In the end, we
57 # just need to get the number of elements of the resulting array.
58 
59 use v5.36;
60 use List::Util qw(uniq);
61 
62 big_and_little_omega(100061,0);
63 big_and_little_omega(971088,0);
64 big_and_little_omega(63640,1);
65 big_and_little_omega(988841,1);
66 big_and_little_omega(211529,0);
67 
68 sub big_and_little_omega($number, $mode) {
69     say "Input: $number, $mode";
70     my @factors = prime_factors($number);
71     @factors = uniq(@factors) unless $mode;
72     say "Output: " . scalar(@factors);
73 }
74 
75 sub prime_factors($number) {
76     my @result = ();
77     foreach my $i (2..$number-1) {
78         if($number % $i == 0) {
79             push @result, $i;
80             push @result, prime_factors($number / $i);
81             return @result;
82         }
83     }
84     push @result, $number;
85     return @result;
86 }
87