28 lines
799 B
Kotlin
28 lines
799 B
Kotlin
fun main() {
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val input = readInputString("day11.txt").split(" ").map { it.toLong() }
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val part1 = input.blink(25)
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println("Part 1: $part1")
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val part2 = input.blink(75)
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println("Part 2: $part2")
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}
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fun List<Long>.blink(count: Int) = fold(0L) { acc, stone -> acc + blink(stone, count) }
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val memo = mutableMapOf<Pair<Long, Int>, Long>()
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fun blink(stone: Long, count: Int): Long = memo.getOrPut(Pair(stone, count)) {
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if (count == 0) return 1
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val str = "$stone"
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val strLen = str.count()
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when {
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stone == 0L -> blink(1L, count - 1)
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strLen % 2 == 0 ->
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blink(str.substring(0, strLen / 2).toLong(), count - 1) +
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blink(str.substring(strLen / 2).toLong(), count - 1)
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else -> blink(stone * 2024, count - 1)
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}
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}
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