Title
a

12/10/2020, 5:32 AM
ok that was… wow (spoilers)
me naively thinking my program will finish running in the next thousand years without caching number values
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``````class Aoc2020Day10 : Problem(2020, 10) {
private val jolts = lines.map { it.toLong() }.sorted()

override fun solvePart1(): Any {
val joltsLeft = jolts.toMutableList().apply { this += jolts.last() + 3 }

var currentJolt = 0L
val distributions = mutableMapOf(*(1..3).map { it to 0 }.toTypedArray())
while (joltsLeft.size >= 1) {
joltsLeft.first { it > currentJolt && it - currentJolt <= 3 }.let { newJolt ->
val difference = (newJolt - currentJolt).toInt()
distributions.replace(difference, distributions[difference]!! + 1)
currentJolt = newJolt
joltsLeft.remove(newJolt)
}
}

return distributions.getValue(1) * distributions.getValue(3)
}

override fun solvePart2(): Any {
val joltToCombinationsMapping = mutableMapOf<Long, Long>()

fun countJoltCombos(curr: Long, joltsLeft: List<Long>): Long {
return when {
joltToCombinationsMapping.containsKey(curr) -> joltToCombinationsMapping.getValue(curr)
joltsLeft.none { it - curr in 1..3 } || joltsLeft.size == 1 && joltsLeft.first() == jolts.maxOrNull()!! -> 1L
else -> {
joltsLeft.filter { it - curr in 1..3 }
.sumOf { v -> countJoltCombos(v, joltsLeft.filter { num -> num > v }).apply { joltToCombinationsMapping[v] = this } }
}
}
}
return countJoltCombos(0, lines.map { it.toLong() })
}
}``````
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