The weekly challenge 312 - Task 2: Balls and Boxes

 1 #!/usr/bin/env perl
 2 # https://theweeklychallenge.org/blog/perl-weekly-challenge-312/#TASK2
 3 #
 4 # Task 2: Balls and Boxes
 5 # =======================
 6 #
 7 # There are $n balls of mixed colors: red, blue or green. They are all
 8 # distributed in 10 boxes labelled 0-9.
 9 #
10 # You are given a string describing the location of balls.
11 #
12 # Write a script to find the number of boxes containing all three colors.
13 # Return 0 if none found.
14 #
15 ## Example 1
16 ##
17 ## Input: $str = "G0B1R2R0B0"
18 ## Output: 1
19 ##
20 ## The given string describes there are 5 balls as below:
21 ## Box 0: Green(G0), Red(R0), Blue(B0) => 3 balls
22 ## Box 1: Blue(B1) => 1 ball
23 ## Box 2: Red(R2) => 1 ball
24 #
25 ## Example 2
26 ##
27 ## Input: $str = "G1R3R6B3G6B1B6R1G3"
28 ## Output: 3
29 ##
30 ## The given string describes there are 9 balls as below:
31 ## Box 1: Red(R1), Blue(B1), Green(G1) => 3 balls
32 ## Box 3: Red(R3), Blue(B3), Green(G3) => 3 balls
33 ## Box 6: Red(R6), Blue(B6), Green(G6) => 3 balls
34 #
35 ## Example 3
36 ##
37 ## Input: $str = "B3B2G1B3"
38 ## Output: 0
39 ##
40 ## Box 1: Green(G1) => 1 ball
41 ## Box 2: Blue(B2)  => 1 ball
42 ## Box 3: Blue(B3)  => 2 balls
43 #
44 ############################################################
45 ##
46 ## discussion
47 ##
48 ############################################################
49 #
50 # As long as we didn't use the full input yet, we pick the first
51 # two characters as color and box and take note of this pair.
52 # In the end, we check all boxes. Every box that has 3 different
53 # colors will be counted towards the result.
54 
55 use v5.36;
56 
57 balls_and_boxes("G0B1R2R0B0");
58 balls_and_boxes("G1R3R6B3G6B1B6R1G3");
59 balls_and_boxes("B3B2G1B3");
60 
61 sub balls_and_boxes($str) {
62    say "Input: \"$str\"";
63    my $boxes = {};
64    while(length($str) > 1) {
65       my ($color, $box);
66       ($color, $box, $str) = split //, $str, 3;
67       $boxes->{$box}->{$color} = 1;
68    }
69    my $result = 0;
70    foreach my $box (keys %$boxes) {
71       my $count = keys %{$boxes->{$box}};
72       $result++ if $count == 3;
73    }
74    say "Output: $result";
75 }