-
Notifications
You must be signed in to change notification settings - Fork 4
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
Showing
3 changed files
with
258 additions
and
2 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
123 changes: 122 additions & 1 deletion
123
2024/kotlin/src/main/kotlin/com/tymscar/day20/part1/part1.kt
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,5 +1,126 @@ | ||
| package com.tymscar.day20.part1 | ||
|
|
||
| import java.util.PriorityQueue | ||
|
|
||
| private enum class EntityType { TRACK, WALL, START, END } | ||
| private data class Position(val x: Int, val y: Int) { | ||
| fun getValidNeighbours(map: Map): List<Position> = listOf( | ||
| Position(x - 1, y), | ||
| Position(x + 1, y), | ||
| Position(x, y - 1), | ||
| Position(x, y + 1) | ||
| ).filter { map.getOrDefault(it, EntityType.WALL) != EntityType.WALL } | ||
|
|
||
| fun getValidCheatPositions(map: Map): List<Position> = listOf( | ||
| Position(x - 2, y), | ||
| Position(x + 2, y), | ||
| Position(x, y - 2), | ||
| Position(x, y + 2) | ||
| ).filter { map.getOrDefault(it, EntityType.WALL) != EntityType.WALL } | ||
| } | ||
|
|
||
| private data class Cheat(val start: Position, val end: Position, val timeSaved: Int) | ||
| private typealias Map = HashMap<Position, EntityType> | ||
| private typealias Path = List<Position> | ||
|
|
||
| private fun getTiming(start: Position, end: Position, map: Map): Int { | ||
| val visited = HashSet<Position>() | ||
| val costs = HashMap<Position, Int>() | ||
| val queue = PriorityQueue<Pair<Position, Int>>(compareBy { it.second }) | ||
|
|
||
| queue.add(start to 0) | ||
| while (queue.isNotEmpty()) { | ||
| val (currPos, currCost) = queue.poll() | ||
| if (currPos == end) return currCost | ||
|
|
||
| if (visited.contains(currPos)) continue | ||
| visited.add(currPos) | ||
|
|
||
| val neighbours = currPos.getValidNeighbours(map) | ||
| for (neighbour in neighbours) { | ||
| if (visited.contains(neighbour)) continue | ||
| val nextCost = currCost + 1 | ||
| if (nextCost < costs.getOrDefault(neighbour, Int.MAX_VALUE)) { | ||
| costs[neighbour] = nextCost | ||
| queue.add(neighbour to nextCost) | ||
| } | ||
| } | ||
| } | ||
| return Int.MAX_VALUE | ||
| } | ||
|
|
||
| private fun getPath(start: Position, end: Position, map: Map): Path { | ||
| val visited = HashSet<Path>() | ||
| val costs = HashMap<Position, Int>() | ||
| val queue = PriorityQueue<Pair<Path, Int>>(compareBy { it.second }) | ||
|
|
||
| queue.add(listOf(start) to 0) | ||
| while (queue.isNotEmpty()) { | ||
| val (currPath, currCost) = queue.poll() | ||
| val currPoint = currPath.last() | ||
| if (currPoint == end) return currPath | ||
|
|
||
| if (visited.contains(currPath)) continue | ||
| visited.add(currPath) | ||
|
|
||
| val neighbours = currPoint.getValidNeighbours(map) | ||
| for (neighbour in neighbours) { | ||
| val neighbourPath = currPath + neighbour | ||
| if (visited.contains(neighbourPath)) continue | ||
| val nextCost = currCost + 1 | ||
| if (nextCost < costs.getOrDefault(neighbour, Int.MAX_VALUE)) { | ||
| costs[neighbour] = nextCost | ||
| queue.add(neighbourPath to nextCost) | ||
| } | ||
| } | ||
| } | ||
| return emptyList() | ||
| } | ||
|
|
||
| private fun getCheats(path: Path, map: Map, memo: HashMap<Position, Int>): List<Cheat> = path | ||
| .flatMapIndexed { i, position -> | ||
| position.getValidCheatPositions(map) | ||
| .map { cheatEndPosition -> | ||
| val cheatTime = when { | ||
| memo.containsKey(cheatEndPosition) -> memo[cheatEndPosition]!! | ||
| else -> getTiming(cheatEndPosition, path.last(), map) | ||
| } | ||
| if (!memo.containsKey(cheatEndPosition)) memo[cheatEndPosition] = cheatTime | ||
| Cheat(position, cheatEndPosition, path.count() - cheatTime - i - 3) | ||
| } | ||
| } | ||
|
|
||
| private fun parseMap(input: String): Map = input | ||
| .lines() | ||
| .flatMapIndexed { i, line -> | ||
| line.mapIndexed { j, char -> | ||
| val position = Position(i, j) | ||
| val type = when (char) { | ||
| '#' -> EntityType.WALL | ||
| '.' -> EntityType.TRACK | ||
| 'S' -> EntityType.START | ||
| 'E' -> EntityType.END | ||
| else -> throw IllegalArgumentException("Invalid character in map: $char") | ||
| } | ||
| position to type | ||
| } | ||
| }.toMap(Map()) | ||
|
|
||
| fun solve(input: String): String { | ||
| return input | ||
| val map = parseMap(input) | ||
| val start = map.entries.find { it.value == EntityType.START }!!.key | ||
| val end = map.entries.find { it.value == EntityType.END }!!.key | ||
| map[start] = EntityType.TRACK | ||
| map[end] = EntityType.TRACK | ||
|
|
||
| val initialTiming = getTiming(start, end, map) | ||
| val initialPath = getPath(start, end, map) | ||
|
|
||
| val memo = initialPath | ||
| .mapIndexed { i, position -> position to (initialTiming - i) } | ||
| .toMap(HashMap()) | ||
|
|
||
| return getCheats(initialPath, map, memo) | ||
| .count { it.timeSaved >= 100 } | ||
| .toString() | ||
| } |
135 changes: 134 additions & 1 deletion
135
2024/kotlin/src/main/kotlin/com/tymscar/day20/part2/part2.kt
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,5 +1,138 @@ | ||
| package com.tymscar.day20.part2 | ||
|
|
||
| import java.util.PriorityQueue | ||
| import kotlin.collections.set | ||
| import kotlin.math.abs | ||
|
|
||
| private const val MAX_CHEAT_DISTANCE = 20 | ||
|
|
||
| private enum class EntityType { TRACK, WALL, START, END } | ||
| private data class Position(val x: Int, val y: Int) { | ||
| fun getValidNeighbours(map: Map): List<Position> = listOf( | ||
| Position(x - 1, y), | ||
| Position(x + 1, y), | ||
| Position(x, y - 1), | ||
| Position(x, y + 1) | ||
| ).filter { map.getOrDefault(it, EntityType.WALL) != EntityType.WALL } | ||
|
|
||
| fun getDistance(other: Position): Int = abs(x - other.x) + abs(y - other.y) | ||
|
|
||
| fun getValidCheatPositions(map: Map): List<Position> = | ||
| (-MAX_CHEAT_DISTANCE..MAX_CHEAT_DISTANCE).flatMap { xOffset -> | ||
| (-MAX_CHEAT_DISTANCE..MAX_CHEAT_DISTANCE).mapNotNull { yOffset -> | ||
| val position = Position(x + xOffset, y + yOffset) | ||
| when { | ||
| xOffset == 0 && yOffset == 0 -> return@mapNotNull null | ||
| this.getDistance(position) > MAX_CHEAT_DISTANCE -> return@mapNotNull null | ||
| else -> position | ||
| } | ||
| } | ||
| }.filter { map.getOrDefault(it, EntityType.WALL) != EntityType.WALL } | ||
| } | ||
|
|
||
| private data class Cheat(val start: Position, val end: Position, val timeSaved: Int) | ||
| private typealias Map = HashMap<Position, EntityType> | ||
| private typealias Path = List<Position> | ||
|
|
||
| private fun getTiming(start: Position, end: Position, map: Map): Int { | ||
| val visited = HashSet<Position>() | ||
| val costs = HashMap<Position, Int>() | ||
| val queue = PriorityQueue<Pair<Position, Int>>(compareBy { it.second }) | ||
|
|
||
| queue.add(start to 0) | ||
| while (queue.isNotEmpty()) { | ||
| val (currPos, currCost) = queue.poll() | ||
| if (currPos == end) return currCost | ||
|
|
||
| if (visited.contains(currPos)) continue | ||
| visited.add(currPos) | ||
|
|
||
| val neighbours = currPos.getValidNeighbours(map) | ||
| for (neighbour in neighbours) { | ||
| if (visited.contains(neighbour)) continue | ||
| val nextCost = currCost + 1 | ||
| if (nextCost < costs.getOrDefault(neighbour, Int.MAX_VALUE)) { | ||
| costs[neighbour] = nextCost | ||
| queue.add(neighbour to nextCost) | ||
| } | ||
| } | ||
| } | ||
| return Int.MAX_VALUE | ||
| } | ||
|
|
||
| private fun getPath(start: Position, end: Position, map: Map): Path { | ||
| val visited = HashSet<Path>() | ||
| val costs = HashMap<Position, Int>() | ||
| val queue = PriorityQueue<Pair<Path, Int>>(compareBy { it.second }) | ||
|
|
||
| queue.add(listOf(start) to 0) | ||
| while (queue.isNotEmpty()) { | ||
| val (currPath, currCost) = queue.poll() | ||
| val currPoint = currPath.last() | ||
| if (currPoint == end) return currPath | ||
|
|
||
| if (visited.contains(currPath)) continue | ||
| visited.add(currPath) | ||
|
|
||
| val neighbours = currPoint.getValidNeighbours(map) | ||
| for (neighbour in neighbours) { | ||
| val neighbourPath = currPath + neighbour | ||
| if (visited.contains(neighbourPath)) continue | ||
| val nextCost = currCost + 1 | ||
| if (nextCost < costs.getOrDefault(neighbour, Int.MAX_VALUE)) { | ||
| costs[neighbour] = nextCost | ||
| queue.add(neighbourPath to nextCost) | ||
| } | ||
| } | ||
| } | ||
| return emptyList() | ||
| } | ||
|
|
||
| private fun getCheats(path: Path, map: Map, memo: HashMap<Position, Int>): List<Cheat> = path | ||
| .flatMapIndexed { i, position -> | ||
| position.getValidCheatPositions(map) | ||
| .map { cheatEndPosition -> | ||
| val cheatTime = when { | ||
| memo.containsKey(cheatEndPosition) -> memo[cheatEndPosition]!! | ||
| else -> getTiming(cheatEndPosition, path.last(), map) | ||
| } | ||
| if (!memo.containsKey(cheatEndPosition)) memo[cheatEndPosition] = cheatTime | ||
| val cheatDistance = position.getDistance(cheatEndPosition) | ||
| Cheat(position, cheatEndPosition, path.count() - cheatTime - i - (1 + cheatDistance)) | ||
| } | ||
| } | ||
|
|
||
| private fun parseMap(input: String): Map = input | ||
| .lines() | ||
| .flatMapIndexed { i, line -> | ||
| line.mapIndexed { j, char -> | ||
| val position = Position(i, j) | ||
| val type = when (char) { | ||
| '#' -> EntityType.WALL | ||
| '.' -> EntityType.TRACK | ||
| 'S' -> EntityType.START | ||
| 'E' -> EntityType.END | ||
| else -> throw IllegalArgumentException("Invalid character in map: $char") | ||
| } | ||
| position to type | ||
| } | ||
| }.toMap(Map()) | ||
|
|
||
| fun solve(input: String): String { | ||
| return input | ||
| val map = parseMap(input) | ||
| val start = map.entries.find { it.value == EntityType.START }!!.key | ||
| val end = map.entries.find { it.value == EntityType.END }!!.key | ||
| map[start] = EntityType.TRACK | ||
| map[end] = EntityType.TRACK | ||
|
|
||
| val initialTiming = getTiming(start, end, map) | ||
| val initialPath = getPath(start, end, map) | ||
|
|
||
| val memo = initialPath | ||
| .mapIndexed { i, position -> position to (initialTiming - i) } | ||
| .toMap(HashMap()) | ||
|
|
||
| return getCheats(initialPath, map, memo) | ||
| .count { it.timeSaved >= 100 } | ||
| .toString() | ||
| } |