From bfee59402eb33f54fef93e785cab3e3a669d0e7a Mon Sep 17 00:00:00 2001
From: Chris Hodges <chrishod@axis.com>
Date: Fri, 22 Dec 2023 10:58:11 +0100
Subject: [PATCH] Minor opt.

Change-Id: Id25e6987382144228afebe661d0b4bdd576b9d6d
---
 src/aoc2023/Day22.kt | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/aoc2023/Day22.kt b/src/aoc2023/Day22.kt
index 5acee1f..bb003ae 100644
--- a/src/aoc2023/Day22.kt
+++ b/src/aoc2023/Day22.kt
@@ -183,7 +183,7 @@ fun main() {
         }
         val disBricks = bricks.filterNot { it.onTopBricks.all { it.uponBricks.size != 1 } }
         val safeBricks = bricks.size - disBricks.size
-        var sum = 0
+        var fallingSum = 0
         for (brick in disBricks) {
             val fallingSet = HashSet<Brick>()
             val removeQueue = ArrayDeque<Brick>()
@@ -192,11 +192,11 @@ fun main() {
             while (removeQueue.isNotEmpty()) {
                 val falling = removeQueue.removeFirst()
                 fallingSet.add(falling)
-                removeQueue.addAll(falling.onTopBricks.filter { it.uponBricks.subtract(fallingSet).isEmpty() })
+                removeQueue.addAll(falling.onTopBricks.filter { fallingSet.containsAll(it.uponBricks) })
             }
-            sum += fallingSet.size - 1
+            fallingSum += fallingSet.size - 1
         }
-        return safeBricks to sum
+        return safeBricks to fallingSum
     }
 
     // test if implementation meets criteria from the description, like: