Challenge 042 task 2

1 files changed, 48 insertions, 0 deletions

diff --git a/challenge-042/jo-37/perl/ch-2.pl b/challenge-042/jo-37/perl/ch-2.pl
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+#!/usr/bin/perl -s
+
+use strict;
+use warnings;
+
+use constant MAX_B => 5;
+
+die <<EOS unless @ARGV == 1;
+usage: $0 N
+
+N
+    generate N random bracket strings, each having a size of 2, 4, 6, 8
+    or 10.  Then check for balanced brackets.
+
+EOS
+
+
+### Input and Output
+
+for (1 .. shift) {
+    my $brackets = gen_brackets();
+    printf "%-10s - %sOK\n", $brackets, 'NOT ' x !check_brackets($brackets);
+}
+
+
+### Implementation
+
+sub gen_brackets {
+    # Generate even sized strings only.
+    my $len = 2 * (1 + int rand MAX_B);
+    # First generate a number having the required number of bits.  Then
+    # translate the bits to brackets.
+    sprintf('%0*b', $len, int rand 2 ** $len) =~ tr/01/()/r;
+}
+
+sub check_brackets {
+    shift =~ m{
+        ^               # anchor start
+        (               # capture subexpression
+            (?:         # non-capturing group
+                \(      # opening bracket
+                (?-1)   # balanced subgroup: recursive regex
+                \)      # closing bracket
+            )*          # repeated bracket embraced balanced group
+        )
+        $               # anchor end
+    }x;
+}