The weekly challenge 316 - Task 1: Circular

 1 #!/usr/bin/env perl
 2 # https://theweeklychallenge.org/blog/perl-weekly-challenge-316/#TASK1
 3 #
 4 # Task 1: Circular
 5 # ================
 6 #
 7 # You are given a list of words.
 8 #
 9 # Write a script to find out whether the last character of each word is the
10 # first character of the following word.
11 #
12 ## Example 1
13 ##
14 ## Input: @list = ("perl", "loves", "scala")
15 ## Output: true
16 #
17 #
18 ## Example 2
19 ##
20 ## Input: @list = ("love", "the", "programming")
21 ## Output: false
22 #
23 #
24 ## Example 3
25 ##
26 ## Input: @list = ("java", "awk", "kotlin", "node.js")
27 ## Output: true
28 #
29 ############################################################
30 ##
31 ## discussion
32 ##
33 ############################################################
34 #
35 # For each element of the list, we pick the first and last character.
36 # If the last character of the previous element matches the first,
37 # everything is still fine and we go to the next element. If there's a
38 # mismatch, we can jump out of the loop right away and return false.
39 # At the end, we can return true.
40 # For the first element, we initialize the "previous last character"
41 # as the first character of the first list element so we don't fall
42 # out of the loop prematurely.
43 
44 use v5.36;
45 circular("perl", "loves", "scala");
46 circular("love", "the", "programming");
47 circular("java", "awk", "kotlin", "node.js");
48 
49 sub circular(@list) {
50     say "Input: (\"" . join("\", \"", @list) . ")";
51     my $prev_char = substr($list[0], 0, 1);
52     foreach my $elem (@list) {
53         my $first = substr($elem, 0, 1);
54         my $last = substr($elem, length($elem) - 1, 1);
55         if($first ne $prev_char) {
56             return say "Output: false";
57         }
58         $prev_char = $last;
59     }
60     say "Output: true";
61 }