blob: 9a15344db1aad68a14b611a3e338b65bfea1127a (
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fun flashSequence(input: Map<Pos2D, Int>) = sequence {
val map = input.toMutableMap()
while (true) {
val flashed = mutableSetOf<Pos2D>()
fun canFlash(entry: Map.Entry<Pos2D, Int>): Boolean = entry.value > 9 && !flashed.contains(entry.key)
// 1)
map.forEach { (pos, energy) -> map[pos] = energy + 1 }
// 2)
while (map.any(::canFlash)) {
map
.filter(::canFlash)
.forEach { (pos, _) ->
flashed.add(pos)
Pos2D.directions8.map { pos + it }.forEach {
if (map.containsKey(it)) {
map[it] = map[it]!! + 1
}
}
}
}
// 3)
flashed.forEach { map[it] = 0 }
yield(flashed.size)
}
}
fun main() {
fun part1(input: List<String>): Int =
flashSequence(parseToMap(input))
.take(100)
.sum()
fun part2(input: List<String>): Int =
flashSequence(parseToMap(input))
.indexOfFirst { it == 100 } + 1
val testInput = readInputAsLines("Day11_test")
check(part1(testInput) == 1656)
check(part2(testInput) == 195)
val input = readInputAsLines("Day11")
println(part1(input))
println(part2(input))
}
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