From 59dfc17ee1d02c1a91f1a936e1015dc7275af16c Mon Sep 17 00:00:00 2001
From: Hubert Van De Walle <hubv@protonmail.com>
Date: Tue, 22 Dec 2020 08:08:13 +0100
Subject: [PATCH] Fix deques order

---
 days/src/main/kotlin/Day22.kt | 43 +++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/days/src/main/kotlin/Day22.kt b/days/src/main/kotlin/Day22.kt
index 41bbbc2..61d893f 100644
--- a/days/src/main/kotlin/Day22.kt
+++ b/days/src/main/kotlin/Day22.kt
@@ -13,33 +13,36 @@ class Day22(@Groups val input: Input<List<List<String>>>) {
     private val two = input.value[1].drop(1).map { it.toInt() }
 
     fun part1(): Long {
-        val oneDeque = ArrayDeque<Int>().apply { one.forEach { addFirst(it) } }
-        val twoDeque = ArrayDeque<Int>().apply { two.forEach { addFirst(it) } }
+        val oneDeque = ArrayDeque(one)
+        val twoDeque = ArrayDeque(two)
 
         while (oneDeque.isNotEmpty() && twoDeque.isNotEmpty()) {
-            val a = oneDeque.removeLast()
-            val b = twoDeque.removeLast()
+            val a = oneDeque.removeFirst()
+            val b = twoDeque.removeFirst()
 
             if (a > b) {
-                oneDeque.addFirst(a)
-                oneDeque.addFirst(b)
+                oneDeque.addLast(a)
+                oneDeque.addLast(b)
             } else {
-                twoDeque.addFirst(b)
-                twoDeque.addFirst(a)
+                twoDeque.addLast(b)
+                twoDeque.addLast(a)
             }
         }
 
         val deque = if (oneDeque.isEmpty()) twoDeque else oneDeque
-        return deque.mapIndexed { index, value -> (index + 1).toLong() * value.toLong() }.sum()
+        return deque.score()
     }
 
+    private fun ArrayDeque<Int>.score() =
+        asReversed().mapIndexed { index, value -> (index + 1).toLong() * value.toLong() }.sum()
+
     fun part2(): Long {
-        val oneDeque = ArrayDeque<Int>().apply { one.forEach { addFirst(it) } }
-        val twoDeque = ArrayDeque<Int>().apply { two.forEach { addFirst(it) } }
+        val oneDeque = ArrayDeque(one)
+        val twoDeque = ArrayDeque(two)
 
         val winner = playGame(oneDeque, twoDeque)
         val deque = if (winner == 1) oneDeque else twoDeque
-        return deque.mapIndexed { index, value -> (index + 1).toLong() * value.toLong() }.sum()
+        return deque.score()
     }
 
     private fun playGame(one: ArrayDeque<Int>, two: ArrayDeque<Int>): Int {
@@ -48,24 +51,24 @@ class Day22(@Groups val input: Input<List<List<String>>>) {
         while (one.isNotEmpty() && two.isNotEmpty()) {
             if (!playedGames.add(PlayedGame(one.toList(), two.toList()))) return 1
 
-            val a = one.removeLast()
-            val b = two.removeLast()
+            val a = one.removeFirst()
+            val b = two.removeFirst()
 
             val winner = when {
                 one.size >= a && two.size >= b -> playGame(
-                    ArrayDeque(one.drop(one.size - a)),
-                    ArrayDeque(two.drop(two.size - b))
+                    ArrayDeque(one.take(a)),
+                    ArrayDeque(two.take(b))
                 )
                 a > b -> 1
                 else -> 2
             }
 
             if (winner == 1) {
-                one.addFirst(a)
-                one.addFirst(b)
+                one.addLast(a)
+                one.addLast(b)
             } else {
-                two.addFirst(b)
-                two.addFirst(a)
+                two.addLast(b)
+                two.addLast(a)
             }
 
         }