76 lines
2.2 KiB
Kotlin
76 lines
2.2 KiB
Kotlin
package be.vandewalleh.aoc.days
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import be.vandewalleh.aoc.utils.input.Day
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import be.vandewalleh.aoc.utils.input.Lines
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import org.eclipse.collections.impl.factory.primitive.IntLists
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import org.eclipse.collections.impl.factory.primitive.IntSets
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@Day(8)
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class Day08(@Lines val input: List<String>) {
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private val instructions = input.map {
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val words = it.split(" ")
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Instruction(Operation.valueOf(words[0].capitalize()), words[1].toInt())
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}.toTypedArray()
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fun part1() = run(instructions).let {
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when (it) {
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is VmResult.Looped -> it.acc
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is VmResult.Terminated -> it.acc
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}
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}
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private fun run(instructions: Array<Instruction>): VmResult {
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var acc = 0
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var ptr = 0
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val visited = IntSets.mutable.empty()
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while (visited.add(ptr)) {
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val instruction = instructions[ptr]
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when (instruction.operation) {
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Operation.Acc -> {
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acc += instruction.argument
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ptr++
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}
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Operation.Jmp -> ptr += instruction.argument
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Operation.Nop -> ptr++
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}
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if (ptr !in instructions.indices) {
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return VmResult.Terminated(acc)
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}
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}
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return VmResult.Looped(acc)
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}
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fun part2(): Int {
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val possibleMutations = IntLists.mutable.empty()
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instructions.forEachIndexed { i, e ->
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if (e.operation == Operation.Jmp || e.operation == Operation.Nop) possibleMutations.add(i)
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}
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for (index in possibleMutations.toArray()) {
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val copy = instructions.copyOf().also {
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val modifiedOperation = if (it[index].operation == Operation.Nop) Operation.Jmp else Operation.Nop
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it[index] = it[index].copy(operation = modifiedOperation)
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}
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val res = run(copy)
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if (res is VmResult.Terminated) return res.acc
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}
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error("No result found")
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}
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}
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private enum class Operation { Acc, Jmp, Nop }
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private data class Instruction(val operation: Operation, val argument: Int)
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private sealed class VmResult {
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data class Looped(val acc: Int) : VmResult()
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data class Terminated(val acc: Int) : VmResult()
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}
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