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  1. #!/usr/bin/perl
  2.  
  3. use strict;
  4. use warnings;
  5.  
  6. # The loop has been added for easy verification of multiple inputs
  7. until (eof) {
  8.     # Read the line with the lengths and convert it into an array
  9.     my $line = <>;
  10.     my @lengths = split /\s+/, $line;
  11.  
  12.     # Create a regex pattern from the lengths. It begins with any number of
  13.     # non 'x' or '_' characters
  14.     my $re = '[x_]*';
  15.     for (@lengths) {
  16.         # Example: if a length was 3, then the pattern will be appended with
  17.         # ([#_]{3})[x_]+ which matches a 3 character combination of '#' and '_'
  18.         # and then 'x's (spaces) or '_'s (unkown characters) after that
  19.         $re .= "([#_]{$_})[x_]+";
  20.     }
  21.  
  22.     # Replace the last + with * since we don't need to have non '#' characters
  23.     # at the end
  24.     $re =~ s/\+$/*/;
  25.  
  26.     # Read the pattern and remove the new line
  27.     my $pat = <>;
  28.     chomp $pat;
  29.  
  30.     # At every index of this array is a concatenation of all patterns that matched
  31.     # the length at that index
  32.     my @matched_parts;
  33.  
  34.     {
  35.         # We need to be less strict to use $$_ (i.e. $1, $2, $3 etc) which are
  36.         # the groups captured during the regex match
  37.         no strict 'refs';
  38.  
  39.         # The complete pattern is matched with the regex generated earlier -
  40.         # hence the ^..$.
  41.         #
  42.         # The code within (?{...}) is executed if the regex matched
  43.         # successfully. Inside the code, we append the matched sub-patterns ($1
  44.         # for the first length, $2 for the second etc) for every length to the
  45.         # right element inside @matched_parts. $$_ will result in $1, $2, $3
  46.         # etc for $_ = 1, 2, 3 etc.
  47.         #
  48.         # The (?!) at the end - i.e. a negative look ahead with no characters -
  49.         # ensures that after the generated regex matches successfully, the
  50.         # complete pattern match still fails, thus forcing the regex engine to
  51.         # backtrack. This way, we iterate over all possible matches of the 1st
  52.         # part and execute the code for them.
  53.         $pat =~ /
  54.                  ^$re$ # match the complete pattern with the constructed regex
  55.                  (?{   # code to execute on successful match. the comma is only added
  56.                        # for clarity
  57.                      $matched_parts[$_-1].=",$$_" for 1..@lengths
  58.                    })
  59.                  (?!)  # fail the match after the code is executed
  60.                 /x;
  61.  
  62.         # Uncomment the following to see the value of @matched_parts
  63.         #use Data::Dumper;
  64.         #$Data::Dumper::Terse = 1;
  65.         #$Data::Dumper::Indent = 3;
  66.         #print "Matched Parts: " . Dumper(\@matched_parts);
  67.     }
  68.  
  69.     if (@matched_parts) {
  70.         # We have a match, so the lengths can be fitted inside the pattern.
  71.         # Now to see if there are any unambiguous matches
  72.         for (0..$#lengths) {
  73.             # For every length, check if @matched_parts does not have any
  74.             # '_' characters in the corresponding index. This means that only
  75.             # '#' characters have matched every time implying that there are
  76.             # no ambiguities. Print such indices.
  77.             print "$_ " if $matched_parts[$_] !~ /_/;
  78.         }
  79.         print "\n";
  80.     } else {
  81.         print "ERROR\n";
  82.     }
  83. }
  84.  
  85.  
Success #stdin #stdout 0s 6132KB
comments (?)
stdin
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3 6 1 4 6
###x######x#x####x######
1 2 1
#____xx___##__x_#
1 2 1
____#___x
1 2 1
#_#x_#
1 2 1
#____#
1 1 1 1
__#_______#____
4 4
______x####________
4 4
__x####________
3
__x__
5 1 3
x#####x____#____
stdout
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0 1 2 3 4 
0 1 2 

ERROR
0 2 


0 
ERROR
0
https://ideone.com/qmEH9G
language:
Perl (perl 5.28.1)
created:
10 years ago
visibility:
public

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