Day 10: Hoof It (#18)

* Day 10: Hoof It (WIP) * Day 10: Hoof It
andilau · Dec 21, 2024 · d1796e8 · d1796e8
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diff --git a/README.md b/README.md
@@ -12,6 +12,7 @@ Advent of Code is an Advent calendar of small programming puzzles by [Eric Wastl
 - Day 5: [Print Queue](https://adventofcode.com/2024/day/5) -- [Day5.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day5.kt)
 - Day 7: [Bridge Repair](https://adventofcode.com/2024/day/7) -- [Day7.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day7.kt)
 - Day 8: [Resonant Collinearity](https://adventofcode.com/2024/day/8) -- [Day8.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day8.kt)
+- Day 10: [Hoof It](https://adventofcode.com/2024/day/10) -- [Day10.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day10.kt)
 - Day 12: [Garden Groups](https://adventofcode.com/2024/day/12) -- [Day12.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day12.kt)
 - Day 14: [Restroom Redoubt](https://adventofcode.com/2024/day/14) -- [Day14.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day14.kt)
 - Day 18: [RAM Run](https://adventofcode.com/2024/day/18) -- [Day18.kt](https://github.com/andilau/advent-of-code-2024/blob/main/src/main/kotlin/days/Day18.kt)

diff --git a/src/main/kotlin/days/Day10.kt b/src/main/kotlin/days/Day10.kt
@@ -0,0 +1,58 @@
+package days
+
+import java.util.PriorityQueue
+
+@AdventOfCodePuzzle(
+    name = "Hoof It",
+    url = "https://adventofcode.com/2024/day/10",
+    date = Date(day = 10, year = 2024)
+)
+class Day10(val input: List<String>) : Puzzle {
+
+    val map: Map<Point, Int> = findAllIgnoring().toMap()
+    val starts: Set<Point> = map.filter { (_, v) -> v == 0 }.keys
+    val exits: Set<Point> = map.filter { (_, v) -> v == 9 }.keys
+
+    override fun partOne() = starts.sumOf { start -> scoreTrail(start, exits) }
+
+    override fun partTwo() = starts.sumOf { start -> scoreTrail2(start, exits) }
+
+    private fun findAllIgnoring(): List<Pair<Point, Int>> = input
+        .flatMapIndexed { y, line -> line.mapIndexedNotNull() { x, c -> if (c.isDigit()) Point(x, y) to c.digitToInt() else null } }
+
+    private fun scoreTrail(start: Point, exits: Set<Point>): Int {
+        var reached = mutableSetOf<Point>()
+        val queue = PriorityQueue<Pair<Point, Int>> { a, b -> a.second.compareTo(b.second) }
+        queue.add(start to 0)
+        val seen = mutableSetOf<Point>()
+
+        while (queue.isNotEmpty()) {
+            val (next, cost) = queue.poll()
+
+            if (next in seen) continue
+            seen += next
+            if (next in exits) reached += next
+            next.neighbors()
+                .filter { it in map }
+                .filter { map[it]!! - map[next]!! == 1 }
+                .forEach { queue.add(it to cost + 1) }
+        }
+        return reached.size
+    }
+
+    private fun scoreTrail2(start: Point, exits: Set<Point>): Int {
+        var reached = mutableListOf<Point>()
+        val queue = PriorityQueue<List<Point>> { a, b -> a.size.compareTo(b.size) }
+        queue.add(listOf(start))
+        while (queue.isNotEmpty()) {
+            val path = queue.poll()
+
+            if (path.last() in exits) reached += path.last()
+            path.last().neighbors()
+                .filter { it in map }
+                .filter { map[it]!! - map[path.last()]!! == 1 }
+                .forEach { queue.add(path + it) }
+        }
+        return reached.size
+    }
+}
diff --git a/src/main/resources/input_day_10.txt b/src/main/resources/input_day_10.txt
@@ -0,0 +1,43 @@
+1089890105678121432132101232127321012354321
+0178763234589030543045000345018018985467610
+3298954103490347656106215496789123876508998
+4567832234321258985287306784100034565012567
+2356541025652767014396454993211239654523498
+1403456710787854320478567884589748703012367
+0512109876598941231569545675679856412721456
+7657238102345410542349830901298764567810565
+8998341201986789621056721850347543201998776
+7087650345679878700876545765456670102367985
+6121065436901263210980238750105985434451234
+5432376327874354890121129653234356321010105
+2345981210965568765430098544234067865430096
+1296590210567809012321107230165123956721187
+0187645323456918456789236109877034847810256
+0099236012567823565018045234578765432901340
+1678107101998894654327102198679896001076541
+2363218900806765785210231087988587123189832
+1454300210712567892104345896107698894898321
+0510321345643498763569856745234565765765410
+9621410478761098954478765030109874327656731
+8734589569454167410349034121918969018549843
+9435678400123256301256121030876878129450652
+4521017312321343214787036980125561034321781
+5670901205430456345698347898234432211289690
+4989874396012387210510256723478934300478541
+3090765487801091234423105410560125410367630
+2101051234945670542394576321021076523458921
+1672340545234987691087689987688987984361010
+0589655676101296789079012896590868970154301
+3438764985054385674108543003481078561567210
+0127123078765676543287632112872369432018923
+6546042129654778904398910001965454342129854
+7237653434569865215897601223450569243036765
+8198548521010764346710510319321678154545678
+9011239630781453454323423408765321069694789
+0100348749692354320345014503455430678783210
+3217654458543765211276769612786726789698701
+8348983267012891200989838764691810652189610
+9456678101101010341234542123500901643076521
+8764569434514567650765430054411898701103430
+7623430127603498769876121069322345632212341
+6510121098012389858789012378443454543303454
diff --git a/src/test/kotlin/SolutionsTest.kt b/src/test/kotlin/SolutionsTest.kt
@@ -16,6 +16,7 @@ class SolutionsTest {
         Day5(InputReader.getInputAsList(5)) to Pair(6041, 4884),
         Day7(InputReader.getInputAsList(7)) to Pair(267566105056L, 116094961956019L),
         Day8(InputReader.getInputAsList(8)) to Pair(371, 1229),
+        Day10(InputReader.getInputAsList(10)) to Pair(501, 1017),
         Day12(InputReader.getInputAsList(12)) to Pair(1464678, 877492),
         Day14(InputReader.getInputAsList(14)) to Pair(214109808L, 7687),
         Day18(InputReader.getInputAsList(18)) to Pair(370, "65,6"),

diff --git a/src/test/kotlin/days/Day10Test.kt b/src/test/kotlin/days/Day10Test.kt
@@ -0,0 +1,124 @@
+package days
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.DynamicTest
+import org.junit.jupiter.api.Nested
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.TestFactory
+
+@DisplayName("Day 10")
+class Day10Test {
+    val trailheadScore1 = """
+        0123
+        1234
+        8765
+        9876""".trimIndent().lines()
+
+    val trailheadScore2 = """
+        ...0...
+        ...1...
+        ...2...
+        6543456
+        7.....7
+        8.....8
+        9.....9""".trimIndent().lines()
+    val trailheadScore3 = """
+        ..90..9
+        ...1.98
+        ...2..7
+        6543456
+        765.987
+        876....
+        987....""".trimIndent().lines()
+    val trailheadScore4 = """
+        10..9..
+        2...8..
+        3...7..
+        4567654
+        ...8..3
+        ...9..2
+        .....01""".trimIndent().lines()
+    val trailheadScore5 = """
+        89010123
+        78121874
+        87430965
+        96549874
+        45678903
+        32019012
+        01329801
+        10456732""".trimIndent().lines()
+
+    @Nested
+    @DisplayName("Part 1")
+    inner class Part1 {
+
+        @TestFactory
+        fun `What is the sum of the scores of all trailheads on your topographic map`() =
+            listOf(
+                trailheadScore1 to 1,
+                trailheadScore2 to 2,
+                trailheadScore3 to 4,
+                trailheadScore4 to 3,
+                trailheadScore5 to 36,
+            ).map { (map, score) ->
+                DynamicTest.dynamicTest("The sum of the scores of all trailheads on the topographic map is $score") {
+                    assertThat(Day10(map).partOne()).isEqualTo(score)
+                }
+            }
+
+    }
+
+    @Nested
+    @DisplayName("Part 2")
+    inner class Part2 {
+
+        val trailheadScore6 = """
+            .....0.
+            ..4321.
+            ..5..2.
+            ..6543.
+            ..7..4.
+            ..8765.
+            ..9....""".trimIndent().lines()
+
+        val trailheadScore7 = """
+            ..90..9
+            ...1.98
+            ...2..7
+            6543456
+            765.987
+            876....
+            987....""".trimIndent().lines()
+
+        val trailheadScore8 = """
+            012345
+            123456
+            234567
+            345678
+            4.6789
+            56789.""".trimIndent().lines()
+        val trailheadScore9 = """
+            89010123
+            78121874
+            87430965
+            96549874
+            45678903
+            32019012
+            01329801
+            10456732""".trimIndent().lines()
+
+        @TestFactory
+        fun `What is the sum of the scores of all trailheads on your topographic map`() =
+            listOf(
+                trailheadScore6 to 3,
+                trailheadScore7 to 13,
+                trailheadScore8 to 227,
+                trailheadScore9 to 81,
+            ).map { (map, score) ->
+                DynamicTest.dynamicTest("The sum of the scores of all trailheads on the topographic map is $score") {
+                    assertThat(Day10(map).partTwo()).isEqualTo(score)
+                }
+            }
+    }
+}