solve 16th day 1st task

0legg · 0legg · commit d8d76602730b · 2024-12-15T21:11:51.000-08:00
diff --git a/year2024/src/main/kotlin/net/olegg/aoc/year2024/day16/Day16.kt b/year2024/src/main/kotlin/net/olegg/aoc/year2024/day16/Day16.kt
@@ -0,0 +1,49 @@
+package net.olegg.aoc.year2024.day16
+
+import net.olegg.aoc.someday.SomeDay
+import net.olegg.aoc.utils.Directions
+import net.olegg.aoc.utils.Directions.Companion.CCW
+import net.olegg.aoc.utils.Directions.Companion.CW
+import net.olegg.aoc.utils.Vector2D
+import net.olegg.aoc.utils.find
+import net.olegg.aoc.utils.get
+import net.olegg.aoc.year2024.DayOf2024
+import java.util.PriorityQueue
+
+/**
+ * See [Year 2024, Day 16](https://adventofcode.com/2024/day/16)
+ */
+object Day16 : DayOf2024(16) {
+  private val empty = setOf('.', 'S', 'E')
+  override fun first(): Any? {
+    val start = matrix.find('S')!!
+    val end = matrix.find('E')!!
+
+    val queue = PriorityQueue<Triple<Vector2D, Directions, Int>>(compareBy { it.third })
+    queue.add(Triple(start, Directions.R, 0))
+    val seen = mutableSetOf<Pair<Vector2D, Directions>>()
+
+    while (queue.isNotEmpty()) {
+      val point = queue.remove()
+      val (curr, dir, length) = point
+      if (curr == end) {
+        return length
+      }
+      val config = curr to dir
+      if (config in seen) {
+        continue
+      }
+      seen += config
+
+      if (matrix[curr + dir.step] in empty) {
+        queue.add(Triple(curr + dir.step, dir, length + 1))
+      }
+      queue.add(Triple(curr, CW[dir]!!, length + 1000))
+      queue.add(Triple(curr, CCW[dir]!!, length + 1000))
+    }
+
+    return -1
+  }
+}
+
+fun main() = SomeDay.mainify(Day16)
