ch-1.pl

1 files changed, 37 insertions, 0 deletions

diff --git a/challenge-042/dave-jacoby/perl5/ch-2.pl b/challenge-042/dave-jacoby/perl5/ch-2.pl
new file mode 100644
index 0000000000..2cb2d701ec
--- /dev/null
+++ b/challenge-042/dave-jacoby/perl5/ch-2.pl
@@ -0,0 +1,37 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw{ say signatures };
+no warnings qw{ experimental::signatures };
+
+# generate the string of braces
+my $string;
+for ( 0 .. 1 + int rand 9 ) {
+	$string .= int rand 2 ? '(' : ')';
+}
+
+# test if the string has matched braces
+my $t = test_braces($string);
+my $response = $t == 0 ? 'OK' : 'NOT OK';
+say qq{$string - $response};
+
+exit;
+
+# The trick is a stack. When you get a "(", 
+# you push onto the stack, and when get a ")",
+# you pop from the stack. We special-case when
+# the stack is empty and we get a ")", immediately
+# returning -1, and then returning the number of 
+# values in the array. A balanced array will return 
+# 0
+
+sub test_braces ( $string ) {
+	my @x;
+	for my $i ( split //, $string ) {
+		return -1 if !scalar @x && $i eq ')';
+		pop @x if scalar @x && $i eq ')';
+		push @x, '' if $i eq '(';
+	}
+	return scalar @x;
+}