From 8d4fd32739f002d49a514bea9a0957fa81cc330e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fredrik=20R=C3=B8dland?= <fmr@finn.no>
Date: Mon, 16 Dec 2024 10:53:36 +0100
Subject: [PATCH] 2024 - Day 16 - part 1

---
 .../kotlin/no/rodland/advent_2024/Day16.kt    | 43 +++++++++++++++----
 .../no/rodland/advent_2024/Day16Test.kt       | 10 +++--
 2 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/src/main/kotlin/no/rodland/advent_2024/Day16.kt b/src/main/kotlin/no/rodland/advent_2024/Day16.kt
index 720b2f58..f73d6c6d 100644
--- a/src/main/kotlin/no/rodland/advent_2024/Day16.kt
+++ b/src/main/kotlin/no/rodland/advent_2024/Day16.kt
@@ -1,27 +1,54 @@
 package no.rodland.advent_2024
 
-import no.rodland.advent.Cave
-import no.rodland.advent.Day
-import no.rodland.advent.toCave
+import no.rodland.advent.*
+import java.util.*
 
 // template generated: 15/12/2024
 // Fredrik Rødland 2024
+data class State(val pos: Pos, val dir: Direction, val cost: Int)
 
-class Day16(val input: List<String>) : Day<Long, Long, Array<CharArray>> {
+class Day16(val input: List<String>) : Day<Int, Int, Cave> {
 
-    private val maze = input.parse()
+    private val parsed = input.parse()
+    private val maze = parsed
 
-    override fun partOne(): Long {
-        return 2
+    override fun partOne(): Int {
+        val shortestPath = dijkstra(maze)
+        return shortestPath
     }
 
-    override fun partTwo(): Long {
+    override fun partTwo(): Int {
         return 2
     }
 
+    private fun dijkstra(maze: Cave): Int {
+        val start = Pos(1, maze.size - 2) // Starting position (S)
+        val end = Pos(maze[0].size - 2, 1) // Ending position (E)
+
+        val pq = PriorityQueue<State>(compareBy { it.cost })
+        val visited = mutableSetOf<Pair<Pos, Direction>>() // Track visited states by Pos and Direction
+
+        pq.add(State(start, Direction.EAST, 0))
+
+        while (pq.isNotEmpty()) {
+            val current = pq.poll()
+            if (!visited.add(Pair(current.pos, current.dir))) continue
+            if (current.pos == end) return current.cost
+
+            val move = current.pos.next(current.dir)
+            if (move in maze && maze[move] != '#') {
+                pq.add(State(move, current.dir, current.cost + 1))
+            }
+            pq.add(State(current.pos, current.dir.left(), current.cost + 1000))
+            pq.add(State(current.pos, current.dir.right(), current.cost + 1000))
+        }
+        return -1 // If no path is found
+    }
+
     override fun List<String>.parse(): Cave {
         return this.toCave()
     }
 
     override val day = "16".toInt()
 }
+
diff --git a/src/test/kotlin/no/rodland/advent_2024/Day16Test.kt b/src/test/kotlin/no/rodland/advent_2024/Day16Test.kt
index db77e3b0..7b37a733 100644
--- a/src/test/kotlin/no/rodland/advent_2024/Day16Test.kt
+++ b/src/test/kotlin/no/rodland/advent_2024/Day16Test.kt
@@ -15,10 +15,10 @@ internal class Day16Test {
     private val data16 = "2024/input_16.txt".readFile()
     private val test16 = "2024/input_16_test.txt".readFile()
 
-    private val resultTestOne = 2L
-    private val resultTestTwo = 2L
-    private val resultOne = 2L
-    private val resultTwo = 2L
+    private val resultTestOne = 7036
+    private val resultTestTwo = 2
+    private val resultOne = 99460
+    private val resultTwo = 2
 
     val test = defaultTestSuiteParseOnInit(
         Day16(data16),
@@ -29,6 +29,8 @@ internal class Day16Test {
         resultTwo,
         { Day16(data16) },
         { Day16(test16) },
+        numTestPart1 = 1,
+        numTestPart2 = 1,
     )
 
     @Nested