X-Git-Url: https://www.fi.muni.cz/~kas/git//home/kas/public_html/git/?a=blobdiff_plain;f=2023%2F43.pl;fp=2023%2F43.pl;h=da408f219f34765a821145b48136d3a490e4b512;hb=d52f1d0570aa59e6dc7ff4034936ca3c1f85b664;hp=0000000000000000000000000000000000000000;hpb=2f3400900f836b8b0b781bc3b0c9a380dd999b6d;p=aoc.git

diff --git a/2023/43.pl b/2023/43.pl
new file mode 100755
index 0000000..da408f2
--- /dev/null
+++ b/2023/43.pl
@@ -0,0 +1,91 @@
+#!/usr/bin/perl -w
+
+use v5.38;
+use experimental 'multidimensional';
+
+my @bricks = map { [ /\d+/g ] } <>;
+my %seen;
+sub set_brick {
+	my ($b) = @_;
+
+	for my $x ($b->[0] .. $b->[3]) {
+	for my $y ($b->[1] .. $b->[4]) {
+	for my $z ($b->[2] .. $b->[5]) {
+		$seen{$x,$y,$z} = 1;
+	} } }
+}
+
+sub clr_brick {
+	my ($b) = @_;
+
+	for my $x ($b->[0] .. $b->[3]) {
+	for my $y ($b->[1] .. $b->[4]) {
+	for my $z ($b->[2] .. $b->[5]) {
+		undef $seen{$x,$y,$z};
+	} } }
+}
+
+sub can_fall {
+	my ($b) = @_;
+
+	return undef if !$b->[5];
+	my $z = $b->[5]-1;
+
+	for my $x ($b->[0] .. $b->[3]) {
+	for my $y ($b->[1] .. $b->[4]) {
+		return undef if $seen{$x,$y,$b->[2]-1};
+	} }
+	return 1;
+}
+
+set_brick($_) for @bricks;
+
+while (1) {
+	my $fallen;
+	my $i = 0;
+	for my $b (@bricks) {
+		$i++;
+		next if !can_fall($b);
+		# say "falling $i (@$b)";
+		clr_brick($b);
+		$b->[2]--; $b->[5]--;
+		set_brick($b);
+		# say "fallen  $i (@$b)";
+		$fallen++;
+	}
+	last if !$fallen;
+}
+
+my $count = 0;
+my (%supported, %supports);
+for my $bi0 (0 .. $#bricks) {
+	my $b0 = $bricks[$bi0];
+	my $cnt = 0;
+	BRICK:
+	for my $bi1 (0 .. $#bricks) {
+		next if $bi0 == $bi1;
+		my $b1 = $bricks[$bi1];
+		# say "possibly supports $bi0 (@$b0) $bi1 (@$b1)";
+		next if $b1->[2] != $b0->[5]+1;
+		for my $x0 ($b0->[0] .. $b0->[3]) {
+		for my $x1 ($b1->[0] .. $b1->[3]) {
+			next if $x0 != $x1;
+			for my $y0 ($b0->[1] .. $b0->[4]) {
+			for my $y1 ($b1->[1] .. $b1->[4]) {
+				next if $y0 != $y1;
+				$supports{$bi0}->{$bi1}++;
+				$supported{$bi1}->{$bi0}++;
+				next BRICK;
+			} }
+		} }
+	}
+}
+SBRICK:
+for my $bi0 (0 .. $#bricks) {
+	for my $bi1 (keys %{ $supports{$bi0} }) {
+		next SBRICK if keys(%{ $supported{$bi1} }) == 1;
+	}
+	$count++;
+}
+
+say $count;