Merge pull request #1131 from dcw803/master

imported my solutions to this week's challenge

3 files changed, 149 insertions, 16 deletions

diff --git a/challenge-042/duncan-c-white/README b/challenge-042/duncan-c-white/README
index 8fe9330cd4..2424e913c2 100644
--- a/challenge-042/duncan-c-white/README
+++ b/challenge-042/duncan-c-white/README
@@ -1,26 +1,35 @@
-Task 1: "Write a script to display attractive numbers between 1 and 50.
+Task 1: "Octal Number System
 
-A number is an attractive number if the number of its prime factors is
-also prime number.
+Write a script to print decimal number 0 to 50 in Octal Number System.
 
-For example: The number 20 is an attractive number, whose prime factors
-are 2, 2 and 5. The total prime factors is 3 which is also a prime number.
+For example:
+Decimal 0 = Octal 0
+Decimal 1 = Octal 1
+Decimal 2 = Octal 2
+Decimal 3 = Octal 3
+Decimal 4 = Octal 4
+Decimal 5 = Octal 5
+Decimal 6 = Octal 6
+Decimal 7 = Octal 7
+Decimal 8 = Octal 10
+
+and so on.
 "
 
-My notes: Think I have a prime-factors finder from an earlier challenge;
-should be easy given that.
+My notes: Trivial.
 
+Task #2: "Balanced Brackets
 
-Task 2: "Write a script to display the first 20 Leonardo Numbers. Read
-https://en.wikipedia.org/wiki/Leonardo_number for more information.
+Write a script to generate a string with random number of ( and ) brackets. Then make the script validate the string if it has balanced brackets.
 
 For example:
-L(0) = 1
-L(1) = 1
-L(2) = L(0) + L(1) + 1 = 3
-L(3) = L(1) + L(2) + 1 = 5
-
-and so on.
+() - OK
+(()) - OK
+)( - NOT OK
+())() - NOT OK
 "
 
-My notes: sounds very nearly as simple as Fibonacci numbers.
+My notes: sounds quite easy. Generate is like coin tossing, validator could
+either count how many nested brackets we're in, or we could use regex search
+and replace to repeatedly delete () pairs of adjacent characters, valid if
+we end up with the empty string.
diff --git a/challenge-042/duncan-c-white/perl5/ch-1.pl b/challenge-042/duncan-c-white/perl5/ch-1.pl
new file mode 100755
index 0000000000..2a5e568a95
--- /dev/null
+++ b/challenge-042/duncan-c-white/perl5/ch-1.pl
@@ -0,0 +1,55 @@
+#!/usr/bin/perl
+#
+# Task 1: "Octal Number System
+# 
+# Write a script to print decimal number 0 to 50 in Octal Number System.
+# 
+# For example:
+# Decimal 0 = Octal 0
+# Decimal 1 = Octal 1
+# Decimal 2 = Octal 2
+# Decimal 3 = Octal 3
+# Decimal 4 = Octal 4
+# Decimal 5 = Octal 5
+# Decimal 6 = Octal 6
+# Decimal 7 = Octal 7
+# Decimal 8 = Octal 10
+# 
+# and so on.
+# "
+# 
+# My notes: Trivial.
+# 
+
+use v5.10;	# to get "say"
+use strict;
+use warnings;
+
+die "Usage: ch-1.pl [N//50]\n" if @ARGV>1;
+
+my $n = shift // 50;
+
+#
+# my $o = to_oct_str( $x );
+#	Convert x to an octal string, eg. 8 is "10"
+#
+sub to_oct_str
+{
+	my( $x ) = @_;
+	my $result = "";
+	if( $x > 7 )
+	{
+		$result = to_oct_str( $x>>3 );
+	}
+	$result .= $x&7;
+	return $result;
+}
+
+
+foreach my $x (0..$n)
+{
+	# convert x to octal..
+	my $o = to_oct_str( $x );
+	say "$x\t$o";
+}
+
diff --git a/challenge-042/duncan-c-white/perl5/ch-2.pl b/challenge-042/duncan-c-white/perl5/ch-2.pl
new file mode 100755
index 0000000000..18710a1533
--- /dev/null
+++ b/challenge-042/duncan-c-white/perl5/ch-2.pl
@@ -0,0 +1,69 @@
+#!/usr/bin/perl
+#
+# Task #2: "Balanced Brackets
+# 
+# Write a script to generate a string with random number of ( and ) brackets. Then make the script validate the string if it has balanced brackets.
+# 
+# For example:
+# () - OK
+# (()) - OK
+# )( - NOT OK
+# ())() - NOT OK
+# "
+# 
+# My notes: sounds quite easy. Generate is like coin tossing, validator
+# could either count how many nested brackets we're in, or we could use
+# regex search and replace to repeatedly delete () pairs of adjacent
+# characters, valid if we end up with the empty string.
+# 
+
+use v5.10;	# to get "say"
+use strict;
+use warnings;
+#use Data::Dumper;
+
+
+#
+# my $brackstr = gen_bracketed_string();
+#	Generate a bracketed string which may or may not
+#	be balanced.
+#
+sub gen_bracketed_string
+{
+	my $len = 20+int(rand(20));
+	my $result="";
+	foreach (1..$len)
+	{
+		$result .= int(rand(2))==0?'(':')';
+	}
+	return $result;
+}
+
+
+#
+# my $isvalid = validate( $brackstr );
+#	Return 1 iff $brackstr is valid, i.e. contains matching
+#	brackets. Else return 0.
+#
+sub validate
+{
+	my( $brackstr ) = @_;
+	my( $origlen, $len );
+	do
+	{
+		$origlen = length($brackstr);
+		$brackstr =~ s/\(\)//g;
+		$len = length($brackstr);
+	} while( $len < $origlen );
+	return $len==0?1:0;
+}
+
+
+srand( $$ ^ time() );
+
+die "Usage: ch-2.pl [BRACKSTR]\n" if @ARGV>1;
+my $brackstr = shift // gen_bracketed_string();
+
+my $isvalid = validate( $brackstr );
+
+say "$brackstr valid? $isvalid";