From 20f20a31799c54953ec516a8e13905e633d1ae97 Mon Sep 17 00:00:00 2001
From: Hubert Van De Walle <hubv@protonmail.com>
Date: Tue, 14 Dec 2021 22:57:05 +0100
Subject: [PATCH] Clean day14

---
 2021/src/main/kotlin/Day14.kt | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/2021/src/main/kotlin/Day14.kt b/2021/src/main/kotlin/Day14.kt
index e877104..3f00a39 100644
--- a/2021/src/main/kotlin/Day14.kt
+++ b/2021/src/main/kotlin/Day14.kt
@@ -12,20 +12,22 @@ class Day14 : BaseDay() {
         val pairs = input.lines.value.drop(2)
             .associate { it.split(" -> ").let { (a, b) -> a to (a[0] + b to b + a[1]) } }
 
-        fun <K> Map<K, Int>.toLong() = mapValues { it.value.toLong() }.toMutableMap()
+        fun <T, K> Grouping<T, K>.toCounter() = eachCount().mapValues { it.value.toLong() }.toMutableMap()
+        fun <K> MutableMap<K, Long>.inc(key: K, count: Long) = compute(key) { _, old -> (old ?: 0) + count }
+        fun <K> MutableMap<K, Long>.dec(key: K, count: Long) = compute(key) { _, old -> (old ?: 0) - count }
 
         // {NN=1, NC=1, CB=1}
-        val polymer = template.windowed(2).groupingBy { it }.eachCount().toLong()
+        val polymer = template.windowed(2).groupingBy { it }.toCounter()
 
         // {N=2, C=1, ...}
-        val counts = template.groupingBy { it }.eachCount().toLong()
+        val counts = template.groupingBy { it }.toCounter()
         repeat(step) {
             polymer.toMap().forEach { (pair, value) ->
                 val (left, right) = pairs[pair]!!
-                polymer[pair]?.let { old -> polymer[pair] = old - value }
-                polymer[left] = (polymer[left] ?: 0) + value
-                polymer[right] = (polymer[right] ?: 0) + value
-                counts[left[1]] = (counts[left[1]] ?: 0) + value
+                polymer.dec(pair, value)
+                polymer.inc(left, value)
+                polymer.inc(right, value)
+                counts.inc(left[1], value)
             }
         }
         return counts.maxOf { it.value } - counts.minOf { it.value }