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Add puzzle solution for 2023, day 23
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| Original file line number | Diff line number | Diff line change |
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| plugins { | ||
| val kotlinVersion: String by System.getProperties() | ||
| val koverVersion: String by System.getProperties() | ||
|
|
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| kotlin("jvm") version kotlinVersion | ||
| id("org.jetbrains.kotlinx.kover") version koverVersion | ||
| } | ||
|
|
||
| dependencies { | ||
| val assertjVersion: String by properties | ||
| val junitJupiterVersion: String by properties | ||
| val junitPlatformVersion: String by properties | ||
|
|
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| api(project(":common:grid")) | ||
| implementation(project(":common:collection")) | ||
| implementation(project(":common:geometry")) | ||
| testImplementation("org.assertj:assertj-core:$assertjVersion") | ||
| testImplementation("org.junit.jupiter:junit-jupiter-api:$junitJupiterVersion") | ||
| testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine:$junitJupiterVersion") | ||
| testRuntimeOnly("org.junit.platform:junit-platform-launcher:$junitPlatformVersion") | ||
| } |
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...ay23/hike/src/main/kotlin/com/curtislb/adventofcode/year2023/day23/hike/HikingTrailMap.kt
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,200 @@ | ||
| package com.curtislb.adventofcode.year2023.day23.hike | ||
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| import com.curtislb.adventofcode.common.collection.arrayQueueOf | ||
| import com.curtislb.adventofcode.common.geometry.Direction | ||
| import com.curtislb.adventofcode.common.geometry.Point | ||
| import com.curtislb.adventofcode.common.grid.Grid | ||
| import com.curtislb.adventofcode.common.grid.forEachPointValue | ||
| import com.curtislb.adventofcode.common.grid.mutableGridOf | ||
| import java.io.File | ||
|
|
||
| /** | ||
| * A 2D grid of tiles representing a collection of interconnected hiking trails that span the height | ||
| * of the grid. | ||
| * | ||
| * @property grid A grid of [Tile]s that makes up the map of hiking trails. The grid must have at | ||
| * least one [Tile.PATH] tile in each of its first and last rows. | ||
| * | ||
| * @throws IllegalArgumentException If the [grid] does not have a [Tile.PATH] tile in each of its | ||
| * first and last rows. | ||
| */ | ||
| class HikingTrailMap(private val grid: Grid<Tile>) { | ||
| /** | ||
| * The position of the starting path tile in the first row of the grid. | ||
| */ | ||
| private val startPosition: Point | ||
|
|
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| /** | ||
| * The position of the goal path tile in the last row of the grid. | ||
| */ | ||
| private val goalPosition: Point | ||
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| init { | ||
| // Find the grid position of the starting path tile | ||
| val startColumnIndex = grid.firstRow().indexOf(Tile.PATH) | ||
| require(startColumnIndex != -1) { "Grid must have a path tile in the first row" } | ||
| startPosition = Point.fromMatrixCoordinates(0, startColumnIndex) | ||
|
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| // Find the grid position of the goal path tile | ||
| val goalColumnIndex = grid.lastRow().indexOf(Tile.PATH) | ||
| require(goalColumnIndex != -1) { "Grid must have a path tile in the last row" } | ||
| goalPosition = Point.fromMatrixCoordinates(grid.lastRowIndex, goalColumnIndex) | ||
| } | ||
|
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| /** | ||
| * Returns the length of the longest walking path from the starting tile (in the first grid row) | ||
| * to the goal tile (in the last grid row), without stepping on the same tile more than once. | ||
| * | ||
| * If there is no walkable path from the starting tile to the goal tile, this function instead | ||
| * returns -1. | ||
| * | ||
| * If [isIcy] is `true`, slope tiles (e.g. [Tile.SLOPE_UP]) are considered to be icy, meaning it | ||
| * is only possible to step onto an adjacent tile in the "downhill" direction for that slope. | ||
| */ | ||
| fun findLongestPathDistance(isIcy: Boolean = true): Int { | ||
| // Find all relevant "waypoints" in the grid | ||
| val waypoints = mutableSetOf(startPosition, goalPosition) | ||
| grid.forEachPointValue { point, char -> | ||
| if (char.isWalkable && isWaypoint(point)) { | ||
| waypoints.add(point) | ||
| } | ||
| } | ||
|
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||
| // Use BFS to construct a "weighted graph" of edges between waypoints | ||
| val waypointEdgesMap = mutableMapOf<Point, MutableMap<Point, Int>>() | ||
| for (source in waypoints) { | ||
| val pointQueue = arrayQueueOf(source) | ||
| val distanceMap = mutableMapOf(source to 0) | ||
| while (pointQueue.isNotEmpty()) { | ||
| val point = pointQueue.poll() | ||
| val distance = distanceMap[point]!! | ||
|
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| // Stop searching along path when a waypoint is found | ||
| if (point in waypoints && point != source) { | ||
| waypointEdgesMap.getOrPut(source) { mutableMapOf() }[point] = distance | ||
| continue | ||
| } | ||
|
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| // Enqueue adjacent tiles that are walkable and unvisited | ||
| for (neighbor in getWalkableNeighbors(point, isIcy)) { | ||
| if (neighbor !in distanceMap) { | ||
| pointQueue.offer(neighbor) | ||
| distanceMap[neighbor] = distance + 1 | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| return maxDistanceToGoal(startPosition, waypointEdgesMap, visitedSet = mutableSetOf()) | ||
| } | ||
|
|
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| /** | ||
| * Returns the positions of all tiles onto which it's possible to step from the tile at the | ||
| * specified grid [position]. | ||
| * | ||
| * If [isIcy] is `true`, slope tiles (e.g. [Tile.SLOPE_UP]) are considered to be icy, meaning it | ||
| * is only possible to step onto an adjacent tile in the "downhill" direction for that slope. | ||
| */ | ||
| private fun getWalkableNeighbors(position: Point, isIcy: Boolean): List<Point> { | ||
| return when (val tile = grid[position]) { | ||
| // Can step from a normal path tile onto any adjacent tile | ||
| Tile.PATH -> position.cardinalNeighbors().filter(::isWalkable) | ||
|
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| // Shouldn't be possible to step onto a forest tile | ||
| Tile.FOREST -> emptyList() | ||
|
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| // Can only step in the "downhill" direction from an icy slope | ||
| Tile.SLOPE_UP, Tile.SLOPE_RIGHT, Tile.SLOPE_DOWN, Tile.SLOPE_LEFT -> { | ||
| if (isIcy) { | ||
| val direction = Direction.fromChar(tile.symbol) | ||
| val neighbor = position.move(direction) | ||
| if (isWalkable(neighbor)) listOf(neighbor) else emptyList() | ||
| } else { | ||
| position.cardinalNeighbors().filter(::isWalkable) | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| /** | ||
| * Returns `true` if it is possible to step onto the tile at the specified grid [position]. | ||
| */ | ||
| private fun isWalkable(position: Point) = grid.getOrNull(position)?.isWalkable == true | ||
|
|
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| /** | ||
| * Returns `true` if the tile at the specified grid [position] satisfies *any* of the following | ||
| * criteria: | ||
| * | ||
| * - It is the starting path tile. | ||
| * - It is the goal path tile. | ||
| * - It is adjacent to 3+ walkable tiles. | ||
| */ | ||
| private fun isWaypoint(position: Point): Boolean { | ||
| return position == startPosition || | ||
| position == goalPosition || | ||
| position.cardinalNeighbors().count(::isWalkable) > 2 | ||
| } | ||
|
|
||
| /** | ||
| * Returns the maximum distance from [source] to the goal position by following weighted edges | ||
| * in the specified [edgesMap] and without visiting any position more than once, including | ||
| * any previously visited positions in the given [visitedSet]. | ||
| * | ||
| * If it is no path from [source] to the goal that satisfies the above conditions, this function | ||
| * instead returns -1. | ||
| */ | ||
| private fun maxDistanceToGoal( | ||
| source: Point, | ||
| edgesMap: Map<Point, Map<Point, Int>>, | ||
| visitedSet: MutableSet<Point> | ||
| ): Int { | ||
| // Distance from the goal to itself is 0 | ||
| if (source == goalPosition) { | ||
| return 0 | ||
| } | ||
|
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| // Set default distance for if no path is found | ||
| var maxDistance = -1 | ||
|
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| // Mark source as visited | ||
| visitedSet.add(source) | ||
|
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| // Check recursively for the maximum distance from all neighbors | ||
| for ((neighbor, distance) in edgesMap[source]!!) { | ||
| // Don't check a previously visited position | ||
| if (neighbor in visitedSet) { | ||
| continue | ||
| } | ||
|
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| // Check distance from neighbor and save it if needed | ||
| val neighborDistance = maxDistanceToGoal(neighbor, edgesMap, visitedSet) | ||
| if (neighborDistance >= 0) { | ||
| maxDistance = maxOf(maxDistance, distance + neighborDistance) | ||
| } | ||
| } | ||
|
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| // Unmark source as visited (backtrack) | ||
| visitedSet.remove(source) | ||
|
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| return maxDistance | ||
| } | ||
|
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| companion object { | ||
| /** | ||
| * Returns an instance of [HikingTrailMap] with the tile grid read from the given [file]. | ||
| * | ||
| * The [file] must contain lines of equal length, where each character represents the [Tile] | ||
| * at the corresponding grid position. | ||
| * | ||
| * @throws IllegalArgumentException If [file] is formatted incorrectly. | ||
| */ | ||
| fun fromFile(file: File): HikingTrailMap { | ||
| val grid = mutableGridOf<Tile>() | ||
| file.forEachLine { line -> | ||
| val row = line.map { Tile.fromChar(it) } | ||
| grid.addShallowRow(row) | ||
| } | ||
| return HikingTrailMap(grid) | ||
| } | ||
| } | ||
| } |
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