Solve Day 25

2024/src/main/kotlin/aoc/year2024/Day25.kt

@@ -0,0 +1,41 @@
+package aoc.year2024
+
+import aoc.library.Puzzle
+
+object Day25 : Puzzle<Int, Unit>(day = 25) {
+
+  override fun solvePart1(input: String): Int {
+    val (keys, locks) = parse(input)
+    return keys.sumOf { key ->
+      locks.count { lock ->
+        keyMatchesLock(key, lock)
+      }
+    }
+  }
+
+  private fun keyMatchesLock(
+    key: List<Int>,
+    lock: List<Int>,
+  ): Boolean = key.zip(lock).all { (k, l) ->
+    k + l <= 5
+  }
+
+  private fun parse(input: String): Pair<List<List<Int>>, List<List<Int>>> {
+    val keys = mutableListOf<List<Int>>()
+    val locks = mutableListOf<List<Int>>()
+    input.split("\n\n").map {
+      val lines = it.lines()
+      val isKey = lines[0][0] == '#'
+      val pins = List(5) { row ->
+        (1..5).count { column ->
+          lines[column][row] == '#'
+        }
+      }
+      if (isKey) keys += pins else locks += pins
+    }
+    return keys to locks
+  }
+
+  override fun solvePart2(input: String) {
+  }
+}

2024/src/test/kotlin/aoc/year2024/Day25Test.kt

@@ -0,0 +1,60 @@
+package aoc.year2024
+
+import aoc.library.solvePart1
+import io.kotest.matchers.ints.shouldBeExactly
+import org.junit.jupiter.api.Test
+
+class Day25Test {
+
+  @Test
+  fun part1TestInput() {
+    Day25.solvePart1(
+      """
+      #####
+      .####
+      .####
+      .####
+      .#.#.
+      .#...
+      .....
+
+      #####
+      ##.##
+      .#.##
+      ...##
+      ...#.
+      ...#.
+      .....
+
+      .....
+      #....
+      #....
+      #...#
+      #.#.#
+      #.###
+      #####
+
+      .....
+      .....
+      #.#..
+      ###..
+      ###.#
+      ###.#
+      #####
+
+      .....
+      .....
+      .....
+      #....
+      #.#..
+      #.#.#
+      #####
+      """.trimIndent(),
+    ) shouldBeExactly 3
+  }
+
+  @Test
+  fun part1() {
+    Day25.solvePart1() shouldBeExactly 3360
+  }
+}