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object Day24 {
@JvmInline
private value class Register private constructor(val address: Int) {
companion object {
val W = Register(0)
val X = Register(1)
val Y = Register(2)
val Z = Register(3)
fun fromString(string: String) = when (string) {
"x" -> X
"y" -> Y
"z" -> Z
"w" -> W
else -> throw IllegalArgumentException(string)
}
}
}
private sealed class Instruction {
companion object {
fun fromString(string: String) = string.split(" ").let { parts ->
val operatorString = parts[0]
val target = Register.fromString(parts[1])
if (operatorString == "inp") {
Input(target)
} else {
val opcode = when (operatorString) {
"add" -> Binary.Opcode.ADD
"mul" -> Binary.Opcode.MUL
"div" -> Binary.Opcode.DIV
"mod" -> Binary.Opcode.MOD
"eql" -> Binary.Opcode.EQL
else -> throw IllegalArgumentException(operatorString)
}
val source = when (val parsed = parts[2].toLongOrNull()) {
is Long -> Source.Literal(parsed)
else -> Source.Memory(Register.fromString(parts[2]))
}
Binary(opcode, target, source)
}
}
}
data class Input(val register: Register) : Instruction()
data class Binary(val opcode: Opcode, val a: Register, val b: Source) : Instruction() {
enum class Opcode {
ADD, MUL, DIV, MOD, EQL
}
}
sealed class Source {
data class Memory(val register: Register) : Source()
data class Literal(val value: Long) : Source()
}
}
private data class ALU(private val memory: LongArray) {
@Suppress("unused")
val w get() = memory[Register.W.address]
@Suppress("unused")
val x get() = memory[Register.X.address]
@Suppress("unused")
val y get() = memory[Register.Y.address]
@Suppress("unused")
val z get() = memory[Register.Z.address]
fun toMutable() = MutableALU(memory.clone())
override fun equals(other: Any?): Boolean {
if (this === other) return true
if (javaClass != other?.javaClass) return false
return memory.contentEquals((other as ALU).memory)
}
override fun hashCode() = memory.contentHashCode()
}
private class MutableALU(private val memory: LongArray) {
constructor() : this(LongArray(4) { 0L })
fun toImmutable() = ALU(memory.clone())
fun executeBatch(batch: List<Instruction.Binary>) {
batch.forEach {
memory[it.a.address] = when (it.opcode) {
Instruction.Binary.Opcode.ADD -> fetch(it.a) + fetch(it.b)
Instruction.Binary.Opcode.MUL -> fetch(it.a) * fetch(it.b)
Instruction.Binary.Opcode.DIV -> fetch(it.a) / fetch(it.b)
Instruction.Binary.Opcode.MOD -> fetch(it.a) % fetch(it.b)
Instruction.Binary.Opcode.EQL -> if (fetch(it.a) == fetch(it.b)) 1L else 0L
}
}
}
fun feedInput(input: Instruction.Input, value: Long) {
memory[input.register.address] = value
}
private fun fetch(register: Register) = memory[register.address]
private fun fetch(source: Instruction.Source) = when (source) {
is Instruction.Source.Literal -> source.value
is Instruction.Source.Memory -> memory[source.register.address]
}
}
private class Program private constructor(private val parts: List<Part>) {
companion object {
fun compileFrom(inputs: List<String>): Program {
val instructionQueue = inputs.map(Instruction::fromString)
val parts = mutableListOf<Part>()
val currentStep = mutableListOf<Instruction.Binary>()
var currentInput: Instruction.Input? = null
instructionQueue.forEach {
when (it) {
is Instruction.Input -> {
parts.add(Part(currentInput, currentStep.toList()))
currentStep.clear()
currentInput = it
}
is Instruction.Binary -> currentStep.add(it)
}
}
parts.add(Part(currentInput, currentStep.toList()))
return Program(parts)
}
}
private data class Part(val input: Instruction.Input?, val instructionBatch: List<Instruction.Binary>)
private data class Checkpoint(val partNumber: Int, val alu: ALU)
fun findInputDigits(
digitRange: IntProgression = 0..9,
successCondition: (ALU) -> Boolean
): Sequence<Long> {
val cache = mutableSetOf<Checkpoint>()
val matchingCheckpoints = mutableSetOf<Checkpoint>()
fun solveRecursively(checkpoint: Checkpoint, accumulator: Long): Sequence<Long> = sequence {
if (cache.contains(checkpoint)) return@sequence
if (checkpoint.partNumber == parts.size) {
if (successCondition(checkpoint.alu)) {
yield(accumulator)
val statesOfCurrent = inputStateSequence(accumulator).toSet()
matchingCheckpoints.addAll(statesOfCurrent)
cache.removeAll(statesOfCurrent)
}
return@sequence
}
digitRange.forEach {
yieldAll(
solveRecursively(
Checkpoint(
checkpoint.partNumber + 1,
executePart(checkpoint.partNumber, checkpoint.alu, it.toLong()),
),
accumulator * 10 + it,
)
)
}
if (!matchingCheckpoints.contains(checkpoint)) cache.add(checkpoint)
Runtime.getRuntime().let {
if (it.totalMemory().toDouble() / it.maxMemory() > 0.75) {
cache.clear()
it.gc()
}
}
}
return solveRecursively(Checkpoint(1, executePart(0)), 0L)
}
private fun inputStateSequence(input: Long) = sequence {
var checkpoint = Checkpoint(1, executePart(0))
yield(checkpoint)
input.toString().toCharArray().map { it.toString().toInt() }.forEach {
checkpoint = Checkpoint(
checkpoint.partNumber + 1,
executePart(checkpoint.partNumber, checkpoint.alu, it.toLong())
)
yield(checkpoint)
}
}
private fun executePart(partNumber: Int, alu: ALU? = null, input: Long? = null): ALU {
val part = parts[partNumber]
val executor = alu?.toMutable() ?: MutableALU()
if (part.input != null && input != null)
executor.feedInput(part.input, input)
executor.executeBatch(part.instructionBatch)
return executor.toImmutable()
}
}
fun bothParts(input: List<String>) = Program
.compileFrom(input)
.findInputDigits(digitRange = 9 downTo 1) { it.z == 0L }
.let { it.first() to it.last() }
}
fun main() {
val input = readInputAsLines("Day24")
val output = Day24.bothParts(input)
println(output.first)
println(output.second)
}
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