The weekly challenge 328 - Task 1: Replace all ?

 1 #!/usr/bin/env perl
 2 # https://theweeklychallenge.org/blog/perl-weekly-challenge-328/#TASK1
 3 #
 4 # Task 1: Replace all ?
 5 # =====================
 6 #
 7 # You are given a string containing only lower case English letters and ?.
 8 #
 9 # Write a script to replace all ? in the given string so that the string
10 # doesn’t contain consecutive repeating characters.
11 #
12 ## Example 1
13 ##
14 ## Input: $str = "a?z"
15 ## Output: "abz"
16 ##
17 ## There can be many strings, one of them is "abz".
18 ## The choices are 'a' to 'z' but we can't use either 'a' or 'z' to replace the '?'.
19 #
20 #
21 ## Example 2
22 ##
23 ## Input: $str = "pe?k"
24 ## Output: "peak"
25 #
26 #
27 ## Example 3
28 ##
29 ## Input: $str = "gra?te"
30 ## Output: "grabte"
31 #
32 ############################################################
33 ##
34 ## discsussion
35 ##
36 ############################################################
37 #
38 # Starting from left to right, we pick each "?" and try to replace it.
39 # For that, we walk the characters from a to z, and if we find one that
40 # works, we use it right away.
41 
42 use v5.36;
43 
44 replace_all("a?z");
45 replace_all("pe?k");
46 replace_all("gra?te");
47 replace_all("gra?te");
48 replace_all("?bc");
49 replace_all("ab?");
50 replace_all("ab?a");
51 replace_all("ab???");
52 replace_all("???a");
53 
54 sub replace_all($str) {
55     say "Input: $str";
56     my @chars = split //, $str;
57     foreach my $i (0..$#chars) {
58         if($chars[$i] eq "?") {
59             foreach my $c ("a".."z") {
60                 my $ok = 1;
61                 if($i != 0) {
62                     if($chars[$i-1] eq $c) {
63                         $ok = 0;
64                     }
65                 }
66                 if($i != $#chars) {
67                     if($chars[$i+1] eq $c) {
68                         $ok = 0;
69                     }
70                 }
71                 if($ok) {
72                     $chars[$i] = $c;
73                     last;
74                 }
75             }
76         }
77     }
78     my $output = join("",@chars);
79     say "Output: $output";
80 }