From 5d0046af83214098fcb93ae28a1a40557a6f1844 Mon Sep 17 00:00:00 2001
From: "Jan \"Yenya\" Kasprzak" <kas@fi.muni.cz>
Date: Mon, 19 Dec 2022 15:27:36 +0100
Subject: [PATCH] Day 19: pruning by remaining time (credits: Honza Obdrzalek)

---
 2022/38.pl | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/2022/38.pl b/2022/38.pl
index f72f5c4..91bc477 100755
--- a/2022/38.pl
+++ b/2022/38.pl
@@ -25,7 +25,7 @@ while (<>) {
 say $prod;
 
 sub dfs($g) {
-	my @q = ([ 0, [ 1, 0, 0, 0 ], [ 0, 0, 0, 0 ], 0, 0 ]);
+	my @q = ([ 32, [ 1, 0, 0, 0 ], [ 0, 0, 0, 0 ], 0, 0 ]);
 	my @needed;
 	for my $rob (0 .. 3) {
 		for my $comp (0 .. 2) {
@@ -39,13 +39,15 @@ sub dfs($g) {
 	while (@q) {
 		my ($t, $robs, $inv, $cantbuy, $didntbuy) = @{ shift @q };
 
-		if ($t++ == 32) {
+		if (!$t) {
 			if ($inv->[3] > $mx) {
 				$mx = $inv->[3];
 				say "   $mx";
 			}
 			next;
 		}
+		next if $t*$robs->[3] + $inv->[3] + ($t*($t-1)/2) <= $mx;
+		$t--;
 
 		my @ni = @$inv;
 		for (0 .. 3) {
@@ -57,12 +59,11 @@ sub dfs($g) {
 			my $bp = $g->[$bpn];
 			my $mask = 1 << $bpn;
 			next if $cantbuy & $mask;
+			next if $didntbuy & $mask;
 			if ($bpn < 3 && $robs->[$bpn] >= $needed[$bpn]) {
 				$cantbuy |= $mask;
 				next;
 			}
-
-			next if $didntbuy & $mask;
 			for (0 .. 2) {
 				next ROBOT if $bp->[$_] > $inv->[$_];
 			}
-- 
2.43.5