Day 10

Author: WVerlaek

src/main/kotlin/y24/Day10.kt

@@ -0,0 +1,38 @@
+package y24
+
+import common.puzzle.solvePuzzle
+import common.puzzle.Input
+import common.puzzle.Puzzle
+import common.datastructures.*
+import common.ext.*
+import common.util.*
+import java.util.*
+import kotlin.math.*
+import kotlin.system.exitProcess
+
+
+fun main() = solvePuzzle(year = 2024, day = 10) { Day10(it) }
+
+class Day10(val input: Input) : Puzzle {
+
+    private fun trails(grid: Grid<Int>, p: Cell<Int>): List<Point> {
+        if (p.value == 9) {
+            return listOf(p.toPoint())
+        }
+
+        return grid.neighbors(p)
+            .filter { it.value == p.value + 1 }
+            .flatMap { trails(grid, it) }
+    }
+
+    private val grid = Grid(input.lines.size, input.lines[0].length) { row, col -> input.lines[row][col].digitToInt() }
+    private val trailHeads = grid.cells().filter { it.value == 0 }
+
+    override fun solveLevel1(): Any {
+        return trailHeads.sumOf { trails(grid, it).distinct().size }
+    }
+
+    override fun solveLevel2(): Any {
+        return trailHeads.sumOf { trails(grid, it).size }
+    }
+}

src/test/kotlin/y24/Day10Test.kt

@@ -0,0 +1,30 @@
+package y24
+
+import common.puzzle.Input
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+internal class Day10Test {
+    private val sample = Input("""
+    89010123
+    78121874
+    87430965
+    96549874
+    45678903
+    32019012
+    01329801
+    10456732
+    """.trimIndent())
+
+    private val day = Day10(sample)
+
+    @Test
+    fun solveLevel1() {
+        assertEquals(36, day.solveLevel1())
+    }
+
+    @Test
+    fun solveLevel2() {
+         assertEquals(81, day.solveLevel2())
+    }
+}