From 8fabb1a70df61a15b75d69439179530b75c1fa67 Mon Sep 17 00:00:00 2001
From: Peter Campbell Smith <pj.campbell.smith@gmail.com>
Date: Wed, 29 Mar 2023 21:26:34 +0100
Subject: Week 210

---
 challenge-210/peter-campbell-smith/blog.txt     |  1 +
 challenge-210/peter-campbell-smith/perl/ch-1.pl | 86 +++++++++++++++++++++++++
 challenge-210/peter-campbell-smith/perl/ch-2.pl | 60 +++++++++++++++++
 3 files changed, 147 insertions(+)
 create mode 100644 challenge-210/peter-campbell-smith/blog.txt
 create mode 100755 challenge-210/peter-campbell-smith/perl/ch-1.pl
 create mode 100755 challenge-210/peter-campbell-smith/perl/ch-2.pl

diff --git a/challenge-210/peter-campbell-smith/blog.txt b/challenge-210/peter-campbell-smith/blog.txt
new file mode 100644
index 0000000000..7cf84c5730
--- /dev/null
+++ b/challenge-210/peter-campbell-smith/blog.txt
@@ -0,0 +1 @@
+http://ccgi.campbellsmiths.force9.co.uk/challenge/210
diff --git a/challenge-210/peter-campbell-smith/perl/ch-1.pl b/challenge-210/peter-campbell-smith/perl/ch-1.pl
new file mode 100755
index 0000000000..2a920972c1
--- /dev/null
+++ b/challenge-210/peter-campbell-smith/perl/ch-1.pl
@@ -0,0 +1,86 @@
+#!/usr/bin/perl
+
+use v5.16;       # The Weekly Challenge - 2023-03-27
+use utf8;        # Week 210 task 1 - Kill and win
+use strict;      # Peter Campbell Smith
+use warnings;    # Blog: http://ccgi.campbellsmiths.force9.co.uk/challenge
+
+my ($best, $max, $j, @test);
+
+kill_and_win(2, 3, 1);
+kill_and_win(1, 1, 2, 2, 2, 3);
+kill_and_win(1, 3, 5, 7);
+kill_and_win(2, 2, 2, 2);
+kill_and_win(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+
+# harder one - 20 random numbers in 0 .. 15
+for $j (0 .. 19) {
+	@test[$j] = int(rand(15));
+}
+kill_and_win(@test);
+
+sub kill_and_win {
+	
+	# does what the challenge says
+	my (@list);
+	
+	@list = @_;
+	$best = 0;
+	$max = 0;
+	
+	# the max possible is the sum of all the list elements and we can stop if we find that
+	$max += $_ for @list;
+	
+	# get the answer and show it
+	kill_one(\@list);	
+	say qq[\nInput:  \@list = (] . join(', ', @list) . qq[)];
+	say qq[Output: $best (max = $max)];
+}
+
+sub kill_one {
+	
+	# finds all options of deleting one entry from list and recurses 
+	my ($option, @list, $j, $k, @new_list, $score, $yes);
+	@list = @{$_[0]};
+	
+	# if we've found a solution that scores $max we can stop
+	return 0 if $best == $max;
+	$score = 0;
+	
+	# take an element to delete (if possible)
+	J: for $j (0 .. scalar @list - 1) {
+		
+		# is this eligible for deletion as there is at least one ± 1
+		$yes = 0;
+		K: for $k (0 .. scalar @list - 1) {
+			if (abs($list[$j] - $list[$k]) == 1) {
+				$yes = 1;
+				last K;
+			}
+		}
+		
+		# not eligible
+		next J unless $yes;
+		
+		# so we can delete $list[$j]
+		$score = $list[$j];
+		
+		# create a new list omitting $j and any element ± 1 from element $j
+		@new_list = ();
+		for $k (0 .. scalar @list - 1) {
+			next if $j == $k;
+			if (abs($list[$j] - $list[$k]) == 1) {
+				$score += $list[$k];
+				next;
+			}
+			push(@new_list, $list[$k]);
+		}
+				
+		# if there are still >1 elements in $new_list, recurse
+		$score += kill_one(\@new_list) if scalar @new_list > 1;
+
+		# save the score if it's the best so far
+		$best = $score if $score > $best;
+	}
+	return $score;
+}
diff --git a/challenge-210/peter-campbell-smith/perl/ch-2.pl b/challenge-210/peter-campbell-smith/perl/ch-2.pl
new file mode 100755
index 0000000000..655f04f351
--- /dev/null
+++ b/challenge-210/peter-campbell-smith/perl/ch-2.pl
@@ -0,0 +1,60 @@
+#!/usr/bin/perl
+
+use v5.16;       # The Weekly Challenge - 2023-03-27
+use utf8;        # Week 210 task 2 - Number collision
+use strict;      # Peter Campbell Smith
+use warnings;    # Blog: http://ccgi.campbellsmiths.force9.co.uk/challenge
+
+my ($j, @list);
+
+number_collision(2, 3, -1);
+number_collision(3, 2, -4);
+number_collision(1, -1);
+number_collision(1, -1, 2, -2, 4, -4);
+number_collision(12, -2, -9, -6, -12, 10, 6, 1, 1, -12, 14);
+
+for $j (0 .. 10) {
+	$list[$j] = int(rand(15)) - 7;
+}
+number_collision(@list);
+
+
+sub number_collision {
+	
+	my (@list, $last, $size, $j, $k);
+	
+	# loop over all the numbers, setting them to 0 if they die
+	@list = @_;
+	while (1) {
+		
+		# loop over values
+		$size = scalar @list;
+		for $j (0 .. $size - 2) {
+			
+			# skip unless this is +ve and next is -ve
+			$k = $j + 1;
+			next unless ($list[$j] > 0 and $list[$k] < 0);
+			
+			# same absolute value - both die
+			if (abs($list[$j]) == abs($list[$k])) {
+				$list[$j] = $list[$k] = 0;
+				
+			# this kills next
+			} elsif (abs($list[$j]) < abs($list[$k])) {
+				$list[$j] = 0;
+				
+			# next kills this
+			} else {
+				$list[$k] = 0;
+			}	
+		}
+		
+		# eliminate zeroes and exit if nothing's changed
+		@list = grep { $_ != 0 } @list;
+		last if scalar @list == $size;
+	}
+
+	# show results
+	say qq[\nInput:  \@list = (] . join(', ', @_) . q[)];
+	say qq[Output: (] . join(', ', @list) . qq[)];
+}
-- 
cgit