The weekly challenge 333 - Task 2: Duplicate Zeros

 1 #!/usr/bin/env perl
 2 # https://theweeklychallenge.org/blog/perl-weekly-challenge-333/#TASK2
 3 #
 4 # Task 2: Duplicate Zeros
 5 # =======================
 6 #
 7 # You are given an array of integers.
 8 #
 9 # Write a script to duplicate each occurrence of zero, shifting the remaining
10 # elements to the right. The elements beyond the length of the original array
11 # are not written.
12 #
13 ## Example 1
14 ##
15 ## Input: @ints = (1, 0, 2, 3, 0, 4, 5, 0)
16 ## Output: (1, 0, 0, 2, 3, 0, 0, 4)
17 ##
18 ## Each zero is duplicated.
19 ## Elements beyond the original length (like 5 and last 0) are discarded.
20 #
21 #
22 ## Example 2
23 ##
24 ## Input: @ints = (1, 2, 3)
25 ## Output: (1, 2, 3)
26 ##
27 ## No zeros exist, so the array remains unchanged.
28 #
29 #
30 ## Example 3
31 ##
32 ## Input: @ints = (1, 2, 3, 0)
33 ## Output: (1, 2, 3, 0)
34 #
35 #
36 ## Example 4
37 ##
38 ## Input: @ints = (0, 0, 1, 2)
39 ## Output: (0, 0, 0, 0)
40 #
41 #
42 ## Example 5
43 ##
44 ## Input: @ints = (1, 2, 0, 3, 4)
45 ## Output: (1, 2, 0, 0, 3)
46 #
47 ############################################################
48 ##
49 ## discussion
50 ##
51 ############################################################
52 #
53 # We just walk from the left of the array to the right. Whenever
54 # we see a "0", we replace the rest of the array by a zero followed
55 # by the rest minus the last element. Of course then we need to skip
56 # the check for "0" in the next iteration so we keep state in a
57 # variable $skip.
58 
59 use v5.36;
60 
61 duplicate_zeros(1, 0, 2, 3, 0, 4, 5, 0);
62 duplicate_zeros(1, 2, 3);
63 duplicate_zeros(1, 2, 3, 0);
64 duplicate_zeros(0, 0, 1, 2);
65 duplicate_zeros(1, 2, 0, 3, 4);
66 
67 sub duplicate_zeros(@ints) {
68     say "Input: (" . join(", ", @ints) . ")";
69     my $skip = 0;
70     foreach my $i (0..$#ints-1) {
71         if($skip) {
72             $skip = 0;
73             next;
74         }
75         if($ints[$i] == 0) {
76             @ints[$i+1..$#ints] = (0, @ints[$i+1..$#ints-1]);
77             $skip = 1;
78         }
79     }
80     say "Output: (" . join(", ", @ints) . ")";
81 }