day(16): add solution
Signed-off-by: Matej Focko <mfocko@redhat.com>
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3 changed files with 253 additions and 0 deletions
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@ -5,6 +5,9 @@ plugins {
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repositories {
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mavenCentral()
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}
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dependencies {
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implementation("org.junit.jupiter:junit-jupiter:5.7.0")
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}
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tasks {
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sourceSets {
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150
src/year2021/day16/Day16.kt
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150
src/year2021/day16/Day16.kt
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@ -0,0 +1,150 @@
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package year2021.day16
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import readInput
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enum class PacketType(val id: Byte) {
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Sum(0),
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Product(1),
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Minimum(2),
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LiteralValue(4),
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Maximum(3),
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GreaterThan(5),
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LessThan(6),
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EqualTo(7),
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}
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enum class LengthType(val id: Byte) {
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TotalLength(0),
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Count(1)
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}
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private fun Byte.toPacketType(): PacketType = PacketType.values().first { it.id == this }
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private fun Byte.toLengthType(): LengthType = LengthType.values().first { it.id == this }
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data class Packet(
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val version: Byte,
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val type: PacketType,
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val bytes: List<Byte> = emptyList(),
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val packets: List<Packet> = emptyList()
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) {
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fun versionSum(): Int = when (type) {
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PacketType.LiteralValue -> version.toInt()
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else -> version.toInt() + packets.sumOf(Packet::versionSum)
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}
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fun eval(): Long = when (type) {
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PacketType.Sum -> packets.sumOf(Packet::eval)
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PacketType.Product -> packets.fold(1) { result, packet -> result * packet.eval() }
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PacketType.Minimum -> packets.minOf(Packet::eval)
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PacketType.LiteralValue -> bytes.fold(0) { result, byte -> result.shl(4).or(byte.toLong()) }
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PacketType.Maximum -> packets.maxOf(Packet::eval)
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PacketType.GreaterThan -> if (packets[0].eval() > packets[1].eval()) 1 else 0
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PacketType.LessThan -> if (packets[0].eval() < packets[1].eval()) 1 else 0
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PacketType.EqualTo -> if (packets[0].eval() == packets[1].eval()) 1 else 0
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}
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}
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fun List<Int>.chunk(from: Int, to: Int): UInt {
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check(to - from <= 32)
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var result = 0u
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var usedBits = 0
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var i = from.div(4)
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// prefix
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if (from.mod(4) != 0) {
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val offset = 4 - from.mod(4)
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val offsetMask = 1.shl(offset) - 1
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result = this[i].and(offsetMask).toUInt()
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usedBits += offset
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i++
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}
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while (4 * i < to) {
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val fromFirst = this[i].toUInt()
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result = result.shl(4).or(fromFirst)
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i++
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usedBits += 4
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}
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return result.shr(usedBits - (to - from))
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}
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fun parseGroups(bytes: List<Int>, groups: MutableList<Byte>, from: Int): Int {
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val mask = (1.shl(4) - 1).toUInt()
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var i = 0
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var lastByte = false
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while (!lastByte) {
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val byte = bytes.chunk(from + 5 * i, from + 5 * (i + 1))
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groups.add(byte.and(mask).toByte())
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i++
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lastByte = byte.shr(4) == 0u
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}
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return from + 5 * i
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}
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fun parsePackets(bytes: List<Int>, packets: MutableList<Packet>, from: Int): Int {
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var index = from + 1
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when (bytes.chunk(from, from + 1).toByte().toLengthType()) {
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LengthType.TotalLength -> {
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val packetsSize = bytes.chunk(index, index + 15).toInt()
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index += 15
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var read = 0
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while (read < packetsSize) {
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val (packet, newIndex) = parsePacket(bytes, index)
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packets.add(packet)
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read += newIndex - index
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index = newIndex
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}
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}
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LengthType.Count -> {
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val packetCount = bytes.chunk(index, index + 11).toInt()
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index += 11
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repeat(packetCount) {
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val (packet, newIndex) = parsePacket(bytes, index)
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packets.add(packet)
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index = newIndex
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}
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}
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}
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return index
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}
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fun parsePacket(bytes: List<Int>, from: Int): Pair<Packet, Int> {
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val version = bytes.chunk(from, from + 3).toByte()
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val typeId = bytes.chunk(from + 3, from + 6).toByte().toPacketType()
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val byteGroups = mutableListOf<Byte>()
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val packets = mutableListOf<Packet>()
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val offset = when (typeId) {
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PacketType.LiteralValue -> parseGroups(bytes, byteGroups, from + 6)
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else -> parsePackets(bytes, packets, from + 6)
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}
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return Pair(Packet(version, typeId, byteGroups, packets), offset)
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}
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fun String.toPacket(): Packet =
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parsePacket(this.map { it.digitToInt(16) }, 0).first
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fun part1(input: String): Int = input.toPacket().versionSum()
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fun part2(input: String): Long = input.toPacket().eval()
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fun main() {
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val input = readInput(16, "input").first()
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println(part1(input))
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println(part2(input))
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}
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100
src/year2021/day16/Day16KtTest.kt
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100
src/year2021/day16/Day16KtTest.kt
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@ -0,0 +1,100 @@
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package year2021.day16
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import org.junit.jupiter.api.Assertions.assertEquals
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import org.junit.jupiter.api.Test
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internal class Day16KtTest {
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@Test
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fun chunkWithOneElement() {
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val list = listOf(15)
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assertEquals(1u, list.chunk(0, 1))
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assertEquals(3u, list.chunk(0, 2))
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assertEquals(7u, list.chunk(0, 3))
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assertEquals(15u, list.chunk(0, 4))
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}
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@Test
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fun chunk() {
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val list = listOf(15, 12, 10, 3)
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assertEquals(15u.shl(4).or(12u).shl(4).or(10u).shl(4).or(3u), list.chunk(0, 16))
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}
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@Test
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fun chunkWholeInt() {
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val list = listOf(15, 12, 10, 3, 6)
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assertEquals(15u.shl(4).or(12u).shl(4).or(10u).shl(4).or(3u).shl(4).or(6u), list.chunk(0, 20))
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}
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@Test
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fun parsing() {
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assertEquals(
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Packet(
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6.toByte(),
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PacketType.LiteralValue,
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bytes = listOf(7, 14, 5).map(Int::toByte),
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),
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"D2FE28".toPacket()
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)
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}
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@Test
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fun part1a() {
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assertEquals(16, part1("8A004A801A8002F478"))
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}
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@Test
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fun part1b() {
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assertEquals(12, part1("620080001611562C8802118E34"))
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}
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@Test
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fun part1c() {
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assertEquals(23, part1("C0015000016115A2E0802F182340"))
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}
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@Test
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fun part1d() {
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assertEquals(31, part1("A0016C880162017C3686B18A3D4780"))
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}
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@Test
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fun part2Sum() {
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assertEquals(3, part2("C200B40A82"))
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}
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@Test
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fun part2Product() {
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assertEquals(54, part2("04005AC33890"))
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}
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@Test
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fun part2Minimum() {
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assertEquals(7, part2("880086C3E88112"))
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}
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@Test
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fun part2Maximum() {
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assertEquals(9, part2("CE00C43D881120"))
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}
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@Test
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fun part2LessThan() {
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assertEquals(1, part2("D8005AC2A8F0"))
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}
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@Test
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fun part2GreaterThan() {
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assertEquals(0, part2("F600BC2D8F"))
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}
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@Test
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fun part2EqualTo() {
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assertEquals(0, part2("9C005AC2F8F0"))
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}
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@Test
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fun part2Complex() {
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assertEquals(1, part2("9C0141080250320F1802104A08"))
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}
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}
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