2024 - Day 18 - part 1&2 - part 2 brute forced (1500ms) - I'm sure th…

…ere is some other way.

src/main/kotlin/no/rodland/advent_2024/Day18.kt

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+package no.rodland.advent_2024
+
+import no.rodland.advent.Day
+import no.rodland.advent.Pos
+
+// template generated: 18/12/2024
+// Fredrik Rødland 2024
+
+class Day18(val input: List<String>, private val bytesToTake: Int, maxIndex: Int) : Day<Int, Pos, List<Pos>> {
+
+    private val parsed = input.parse()
+    private val start = Pos(0, 0)
+    private val end = Pos(maxIndex, maxIndex)
+
+    override fun partOne(): Int {
+        return bfs(bytesToTake).size - 1
+    }
+
+    override fun partTwo(): Pos {
+        val idx = (bytesToTake..parsed.size).first { n ->
+            bfs(n).isEmpty()
+        }
+        return parsed[idx - 1]
+    }
+
+    private fun bfs(n: Int, set: Set<Pos> = parsed.take(n).toSet()) = bfs(start, end, { p ->
+        p.neighbourCellsUDLR()
+            .filter { it !in set }
+            .filter { it.x >= start.x }
+            .filter { it.y >= start.y }
+            .filter { it.x <= end.x }
+            .filter { it.y <= end.y }
+    })
+
+    private fun bfs(
+        start: Pos,
+        end: Pos,
+        nextFunction: (Pos) -> List<Pos>,
+        queue: ArrayDeque<List<Pos>> = ArrayDeque(listOf(listOf(start))),
+        visited: MutableSet<Pos> = mutableSetOf(start)
+    ): List<Pos> {
+        if (queue.isEmpty()) return emptyList()
+        // Dequeue the current path
+        val path = queue.removeFirst()
+        val current = path.last()
+
+        // Check if we reached the end position
+        if (current == end) return path
+
+        // Explore neighbors
+        for (neighbor in nextFunction(current)) {
+            if (!visited.contains(neighbor)) {
+                visited.add(neighbor)
+                queue.add(path + neighbor) // Enqueue the new path
+            }
+        }
+
+        // Recursive call with the updated queue and visited set
+        return bfs(start, end, nextFunction, queue, visited)
+    }
+
+    override fun List<String>.parse(): List<Pos> {
+        return map { line ->
+            val (first, second) = line.split(",").map { it.toInt() }
+            Pos(first, second)
+        }
+    }
+
+    override val day = "18".toInt()
+}

src/test/kotlin/no/rodland/advent_2024/Day18Test.kt

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+package no.rodland.advent_2024
+
+import no.rodland.advent.*
+import org.junit.jupiter.api.Nested
+import org.junit.jupiter.api.Test
+import readFile
+
+//
+//  run: download_aoc_input.sh to download input
+//
+
+@Suppress("ClassName")
+@DisableSlow
+internal class Day18Test {
+    private val data18 = "2024/input_18.txt".readFile()
+    private val test18 = "2024/input_18_test.txt".readFile()
+
+    private val resultTestOne = 22
+    private val resultTestTwo = Pos(6,1)
+    private val resultOne = 286
+    private val resultTwo = Pos(20,64)
+
+    val test = defaultTestSuiteParseOnInit(
+        Day18(data18, 1024, 70),
+        Day18(test18, 12, 6),
+        resultTestOne,
+        resultOne,
+        resultTestTwo,
+        resultTwo,
+        { Day18(data18, 1024, 70) },
+        { Day18(test18, 12, 6) },
+        numTestPart1 = 20,
+        numTestPart2 = 1
+    )
+
+    @Nested
+    inner class Init {
+        @Test
+        fun `18,-,example,1`() {
+            report(AOCTest({ "123".toInt() }, Unit, 123, 5, "18".toInt(), Part.TWO, false, "example"))
+        }
+
+        @Test
+        fun `18,-,example,2`() {
+            report(test.initTest.copy())
+        }
+
+        @Test
+        fun `18,-,test,init`() {
+            report(test.initTest)
+        }
+
+        @Test
+        fun `18,-,live,init`() {
+            report(test.initLive)
+        }
+    }
+
+    @Nested
+    inner class `Part 1` {
+        @Test
+        fun `18,1,test`() {
+            report(test.testPart1)
+        }
+
+        @Test
+        fun `18,1,live,1`() {
+            report(test.livePart1)
+        }
+    }
+
+    @Nested
+    inner class `Part 2` {
+        @Test
+        fun `18,2,test`() {
+            report(test.testPart2)
+        }
+
+        @Test
+        @Slow(1500)
+        fun `18,2,live,1`() {
+            report(test.livePart2)
+        }
+    }
+}

src/test/resources/2024/input_18_test.txt

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+5,4
+4,2
+4,5
+3,0
+2,1
+6,3
+2,4
+1,5
+0,6
+3,3
+2,6
+5,1
+1,2
+5,5
+2,5
+6,5
+1,4
+0,4
+6,4
+1,1
+6,1
+1,0
+0,5
+1,6
+2,0