aboutsummaryrefslogtreecommitdiff
path: root/aoc-2021-kotlin/src/Day14.kt
diff options
context:
space:
mode:
Diffstat (limited to 'aoc-2021-kotlin/src/Day14.kt')
-rw-r--r--aoc-2021-kotlin/src/Day14.kt46
1 files changed, 46 insertions, 0 deletions
diff --git a/aoc-2021-kotlin/src/Day14.kt b/aoc-2021-kotlin/src/Day14.kt
new file mode 100644
index 0000000..920ea9e
--- /dev/null
+++ b/aoc-2021-kotlin/src/Day14.kt
@@ -0,0 +1,46 @@
+object Day14 {
+ private fun getPolymerLetterCounts(input: List<String>, iterations: Int): Long {
+ val template = input.first()
+ val rules = input.drop(2).associate {
+ val (pattern, replacement) = it.split(" -> ")
+ (pattern[0] to pattern[1]) to replacement.first()
+ }
+
+ var pairCounts = template
+ .zipWithNext()
+ .groupingBy { it }
+ .eachCount()
+ .mapValues { (_, v) -> v.toLong() }
+
+ repeat(iterations) {
+ val newCounts = mutableMapOf<Pair<Char, Char>, Long>()
+
+ pairCounts.forEach { (pair, count) ->
+ newCounts.merge(rules[pair]!! to pair.second, count, Long::plus)
+ newCounts.merge(pair.first to rules[pair]!!, count, Long::plus)
+ }
+
+ pairCounts = newCounts
+ }
+
+ val letterCounts = mutableMapOf<Char, Long>()
+ pairCounts.forEach { (pair, count) -> letterCounts.merge(pair.second, count, Long::plus) }
+ letterCounts.merge(template.first(), 1, Long::plus)
+
+ return letterCounts.values.let { it.maxOrNull()!! - it.minOrNull()!! }
+ }
+
+ fun part1(input: List<String>): Long = getPolymerLetterCounts(input, 10)
+
+ fun part2(input: List<String>): Long = getPolymerLetterCounts(input, 40)
+}
+
+fun main() {
+ val testInput = readInputAsLines("Day14_test")
+ check(Day14.part1(testInput) == 1588L)
+ check(Day14.part2(testInput) == 2188189693529L)
+
+ val input = readInputAsLines("Day14")
+ println(Day14.part1(input))
+ println(Day14.part2(input))
+}