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Diffstat (limited to 'aoc-2021-kotlin/src/Day14.kt')
-rw-r--r-- | aoc-2021-kotlin/src/Day14.kt | 46 |
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)) +} |