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(Slow) solution 2018-15, part 1 (Beverage Bandits)
A solution that makes the tests pass but is much too slow for the real puzzle input.
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‎src/main/kotlin/de/ronny_h/aoc/extensions/grids/Coordinates.kt‎

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@@ -35,6 +35,9 @@ data class Coordinates(val row: Int, val col: Int) : Comparable<Coordinates> {
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override fun toString() = "($row,$col)"
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/**
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* Orders [Coordinates] in reading order: top-to-bottom, then left-to-right.
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*/
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override fun compareTo(other: Coordinates): Int {
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if (this.row == other.row) {
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return this.col - other.col

‎src/main/kotlin/de/ronny_h/aoc/year2018/day15/BeverageBandits.kt‎

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package de.ronny_h.aoc.year2018.day15
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import de.ronny_h.aoc.AdventOfCode
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import de.ronny_h.aoc.extensions.collections.filterMinBy
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import de.ronny_h.aoc.extensions.graphs.ShortestPath
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import de.ronny_h.aoc.extensions.grids.Coordinates
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import de.ronny_h.aoc.extensions.grids.SimpleCharGrid
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import de.ronny_h.aoc.year2018.day15.CombatArea.PlayerType.Elf
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import de.ronny_h.aoc.year2018.day15.CombatArea.PlayerType.Goblin
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import io.github.oshai.kotlinlogging.KotlinLogging
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private val logger = KotlinLogging.logger {}
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fun main() = BeverageBandits().run(0, 0)
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class BeverageBandits : AdventOfCode<Long>(2018, 15) {
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override fun part1(input: List<String>): Long {
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val combatArea = CombatArea(input)
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while (combatArea.takeOneRound()) {
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// the action takes place in the condition
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}
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return combatArea.outcome()
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}
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override fun part2(input: List<String>): Long {
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return 0
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}
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}
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class CombatArea(input: List<String>) : SimpleCharGrid(input) {
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private val cavern = '.'
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private data class Player(
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val type: PlayerType,
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var position: Coordinates,
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val attackPower: Int = 3,
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var hitPoints: Int = 200
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)
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private enum class PlayerType(val char: Char) {
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Elf('E'), Goblin('G')
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}
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private val units = buildList {
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forEachCoordinates { position, square ->
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when (square) {
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Elf.char -> add(Player(Elf, position))
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Goblin.char -> add(Player(Goblin, position))
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}
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}.last()
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}.toMutableList()
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private var fullRounds = 0L
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/**
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* @return if combat continues
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*/
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fun takeOneRound(): Boolean {
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if (fullRounds % 10 == 0L) logStats()
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units.sortedBy { it.position }.forEach { unit ->
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logger.debug { "unit $unit" }
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val enemyType = if (unit.type == Elf) Goblin else Elf
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val targets = units.filter { it.type == enemyType }
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if (targets.isEmpty()) {
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return false
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}
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unit.move(targets)
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unit.attack(targets)
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}
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fullRounds++
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return true
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}
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fun outcome(): Long = fullRounds * units.sumOf { it.hitPoints }
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private data class Target(val position: Coordinates, val path: ShortestPath<Coordinates>)
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private fun Player.move(
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targets: List<Player>
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) {
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logger.debug { " moving $this" }
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if (targets.any { it.position in position.neighbours() }) {
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// already in range of a target
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return
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}
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val targetsWithPaths = targets.flatMap { target ->
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target.position.neighbours()
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.filter { getAt(it) == cavern }
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.flatMap { inRange ->
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shortestPaths(position, inRange) { neighbour ->
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getAt(neighbour) == cavern
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}
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.map { Target(inRange, it) }
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}
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}
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if (targetsWithPaths.isEmpty()) {
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// no path to any target found
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return
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}
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logger.debug { " ${targetsWithPaths.size} paths found" }
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val nearestTargetPath = targetsWithPaths
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.filterMinBy { it.path.distance }
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.filterMinBy { it.position }
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.filterMinBy { it.path.path[1] }
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.first()
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moveTo(nearestTargetPath.path.path[1])
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}
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private fun Player.attack(targets: List<Player>) {
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logger.debug { " attacking with $this" }
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val opponent = position
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.neighbours()
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.mapNotNull { neighbour -> targets.firstOrNull { it.position == neighbour } }
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.filterMinBy { it.hitPoints }
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.minByOrNull { it.position }
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if (opponent == null) return
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logger.debug { " hitting $opponent" }
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opponent.hitPoints -= attackPower
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if (opponent.hitPoints <= 0) {
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opponent.die()
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}
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}
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private fun Player.moveTo(newPosition: Coordinates) {
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logger.debug { " moving to $newPosition" }
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setAt(position, cavern)
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setAt(newPosition, type.char)
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position = newPosition
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}
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private fun Player.die() {
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setAt(position, cavern)
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units.remove(this)
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}
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private fun logStats() {
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logger.info { "round $fullRounds: ${elfCount()} elfs, ${goblinCount()} goblins" }
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logger.debug { "\n${toString()}" }
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}
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private fun elfCount() = units.count { it.type == Elf }
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private fun goblinCount() = units.count { it.type == Goblin }
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}

‎src/test/kotlin/de/ronny_h/aoc/year2018/day15/BeverageBanditsTest.kt‎

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package de.ronny_h.aoc.year2018.day15
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import de.ronny_h.aoc.extensions.asList
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import io.kotest.core.spec.style.StringSpec
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import io.kotest.matchers.shouldBe
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class BeverageBanditsTest : StringSpec({
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"input can be parsed" {
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val input = """
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#######
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#E..G.#
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#...#.#
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#.G.#G#
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#######
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""".asList()
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CombatArea(input).toString().asList() shouldBe input
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}
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val input = """
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#######
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#.G...#
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#...EG#
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#.#.#G#
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#..G#E#
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#.....#
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#######
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""".asList()
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"movements of two rounds of a small example" {
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val expected1 = """
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#######
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#..G..#
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#...EG#
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#.#G#G#
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#...#E#
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#.....#
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#######
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""".trimIndent()
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val expected2 = """
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#######
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#...G.#
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#..GEG#
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#.#.#G#
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#...#E#
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#.....#
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#######
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""".trimIndent()
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val combatArea = CombatArea(input)
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combatArea.takeOneRound() shouldBe true
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combatArea.toString() shouldBe expected1
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combatArea.takeOneRound() shouldBe true
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combatArea.toString() shouldBe expected2
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}
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"combat of a small example" {
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val expected23 = """
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#######
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#...G.#
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#..G.G#
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#.#.#G#
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#...#E#
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#.....#
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#######
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""".trimIndent()
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val expected24 = """
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#######
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#..G..#
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#...G.#
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#.#G#G#
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#...#E#
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#.....#
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#######
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""".trimIndent()
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val expected25 = """
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#######
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#.G...#
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#..G..#
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#.#.#G#
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#..G#E#
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#.....#
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#######
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""".trimIndent()
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val expected28 = """
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#######
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#G....#
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#.G...#
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#.#.#G#
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#...#E#
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#....G#
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#######
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""".trimIndent()
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val expected47 = """
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#######
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#G....#
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#.G...#
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#.#.#G#
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#...#.#
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#....G#
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#######
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""".trimIndent()
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val combatArea = CombatArea(input)
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repeat(23) { combatArea.takeOneRound() shouldBe true }
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combatArea.toString() shouldBe expected23
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combatArea.takeOneRound() shouldBe true
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combatArea.toString() shouldBe expected24
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combatArea.takeOneRound() shouldBe true
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combatArea.toString() shouldBe expected25
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repeat(3) { combatArea.takeOneRound() shouldBe true }
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combatArea.toString() shouldBe expected28
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repeat(19) { combatArea.takeOneRound() shouldBe true }
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combatArea.toString() shouldBe expected47
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combatArea.takeOneRound() shouldBe false
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}
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"part 1: the outcome of the battle of the small example" {
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BeverageBandits().part1(input) shouldBe 27730
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}
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"part 2" {
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val input = listOf("")
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BeverageBandits().part2(input) shouldBe 0
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}
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})

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