days 5-11

6/1.pl

@@ -0,0 +1,83 @@
+#!/usr/bin/perl
+
+use strict;
+use v5.10;
+use Data::Dumper;
+
+chomp (my @data = <STDIN>);
+@data = sort @data;
+
+my (@x, @y);
+foreach my $coord (@data) {
+    my ($x, $y) = split /, /, $coord;
+    push @x, $x;
+    push @y, $y;
+}
+@x = sort { $a <=> $b } @x;
+@y = sort { $a <=> $b } @y;
+
+my $minX = $x[0];
+my $minY = $y[0];
+my $maxX = $x[$#x];
+my $maxY = $y[$#y];
+
+my %infinite;
+my %count;
+for ( my $y = $minY; $y <= $maxY; $y++ ) {
+    for ( my $x = $minX; $x <= $maxX; $x++ ) {
+        # work out distances
+        
+        my $closest = closest($x, $y, \@data);
+        $count{$closest}++;
+        #say "$x, $y, ", $closest;
+
+        # establish 'infinite' areas
+        if ( $closest && (($x == $minX) || ($x == $maxX)
+             || ($y == $minY) || ($y == $maxY)) ) {
+            $infinite{$closest}++
+        }
+    }
+}
+
+my @best = sort { $count{$b} <=> $count{$a} } keys %count; 
+foreach my $b (@best) { 
+    if ($infinite{$b}) {
+        next;
+    } else {
+        say "$b $count{$b}";
+        exit;
+    }
+}
+
+
+sub closest($$$) {
+    my ($x, $y, $coords) = @_;
+    my %result;
+
+    foreach my $c (@$coords) {
+        my ($cx, $cy) = split /, /, $c;
+
+        my ($xdiff, $ydiff);
+        if ($x < $cx) {
+            $xdiff = $cx - $x;
+        } else {
+            $xdiff = $x - $cx;
+        }
+
+        if ($y < $cy) {
+            $ydiff = $cy - $y;
+        } else {
+            $ydiff = $y - $cy;
+        }
+
+        $result{$c} = ($xdiff + $ydiff);        
+    }
+
+    my @best = sort { $result{$a} <=> $result{$b} } keys %result; 
+    if ($result{$best[0]} == $result{$best[1]}) {
+        return undef;
+    } else {
+        return $best[0];
+    }
+
+}

6/2.pl

@@ -0,0 +1,64 @@
+#!/usr/bin/perl
+
+use strict;
+use v5.10;
+use Data::Dumper;
+
+chomp (my @data = <STDIN>);
+@data = sort @data;
+
+my (@x, @y);
+foreach my $coord (@data) {
+    my ($x, $y) = split /, /, $coord;
+    push @x, $x;
+    push @y, $y;
+}
+@x = sort { $a <=> $b } @x;
+@y = sort { $a <=> $b } @y;
+
+my $minX = $x[0];
+my $minY = $y[0];
+my $maxX = $x[$#x];
+my $maxY = $y[$#y];
+
+my $count;
+for ( my $y = $minY; $y <= $maxY; $y++ ) {
+    for ( my $x = $minX; $x <= $maxX; $x++ ) {
+        # work out distances
+        
+        my $closest = closest($x, $y, \@data);
+        # this assumes there's only a single region, but that seems to be the case here.
+        if ($closest < 10000) {
+            $count++;
+        }
+    }
+}
+
+say $count;
+
+
+sub closest($$$) {
+    my ($x, $y, $coords) = @_;
+    my $result;
+
+    foreach my $c (@$coords) {
+        my ($cx, $cy) = split /, /, $c;
+
+        my ($xdiff, $ydiff);
+        if ($x < $cx) {
+            $xdiff = $cx - $x;
+        } else {
+            $xdiff = $x - $cx;
+        }
+
+        if ($y < $cy) {
+            $ydiff = $cy - $y;
+        } else {
+            $ydiff = $y - $cy;
+        }
+
+        $result += ($xdiff + $ydiff);        
+    }
+    return $result;
+
+}

6/sample.txt

@@ -0,0 +1,6 @@
+1, 1
+1, 6
+8, 3
+3, 4
+5, 5
+8, 9