[2024/7] Bridge Repair (Part 2)

pfolta · Dec 7, 2024 · 2058e07 · 2058e07
1 parent a52ef94
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Showing 3 changed files with 20 additions and 10 deletions.
diff --git a/README.md b/README.md
@@ -28,7 +28,7 @@
 |     2021 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |        |   ★    |   ★    |        |        |        |        |        |        |        |        |        |        |        |    26 |
 |     2022 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |   ★    |   ★    |        |        |        |        |        |        |        |   ☆    |        |        |        |   ☆    |    28 |
 |     2023 |   ★   |   ★   |   ★   |   ★   |   ☆   |   ★   |   ☆   |       |       |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |    12 |
-|     2024 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ☆   |       |       |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |    13 |
+|     2024 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |       |       |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |    14 |
 
 ## 🛷 How to run
 
@@ -170,7 +170,7 @@ e.g. `HandyHaversacks`)*
 |                                           |   4 | [Ceres Search](https://adventofcode.com/2024/day/4)                                                    | [[Code](src/main/kotlin/adventofcode/year2024/Day04CeresSearch.kt)]&nbsp;[[Test](src/test/kotlin/adventofcode/year2024/Day04CeresSearchSpec.kt)]                                             | `2483`                 | `1925`                                           |
 |                                           |   5 | [Print Queue](https://adventofcode.com/2024/day/5)                                                     | [[Code](src/main/kotlin/adventofcode/year2024/Day05PrintQueue.kt)]&nbsp;[[Test](src/test/kotlin/adventofcode/year2024/Day05PrintQueueSpec.kt)]                                               | `6498`                 | `5017`                                           |
 |                                           |   6 | [Guard Gallivant](https://adventofcode.com/2024/day/6)                                                 | [[Code](src/main/kotlin/adventofcode/year2024/Day06GuardGallivant.kt)]&nbsp;[[Test](src/test/kotlin/adventofcode/year2024/Day06GuardGallivantSpec.kt)]                                       | `5212`                 | `1767`                                           |
-|                                           |   7 | [Bridge Repair](https://adventofcode.com/2024/day/7)                                                   | [[Code](src/main/kotlin/adventofcode/year2024/Day07BridgeRepair.kt)]&nbsp;[[Test](src/test/kotlin/adventofcode/year2024/Day07BridgeRepairSpec.kt)]                                           | `8401132154762`        |                                                  |
+|                                           |   7 | [Bridge Repair](https://adventofcode.com/2024/day/7)                                                   | [[Code](src/main/kotlin/adventofcode/year2024/Day07BridgeRepair.kt)]&nbsp;[[Test](src/test/kotlin/adventofcode/year2024/Day07BridgeRepairSpec.kt)]                                           | `8401132154762`        | `95297119227552`                                 |
 
 ## 🕯️ Useful commands
 

diff --git a/src/main/kotlin/adventofcode/year2024/Day07BridgeRepair.kt b/src/main/kotlin/adventofcode/year2024/Day07BridgeRepair.kt
@@ -4,21 +4,31 @@ import adventofcode.Puzzle
 import adventofcode.PuzzleInput
 
 class Day07BridgeRepair(customInput: PuzzleInput? = null) : Puzzle(customInput) {
-    override fun partOne() =
+    private val equations by lazy {
         input
             .lines()
-            .mapNotNull { equation ->
-                val result = equation.split(": ").first().toLong()
-                val numbers = equation.split(": ").last().split(" ").map(String::toLong)
+            .map { equation ->
+                val (result, numbers) = equation.split(": ")
+                result.toLong() to numbers.split(" ").map(String::toLong)
+            }
+    }
+
+    override fun partOne() = equations.calibrationResult(setOf({ a, b -> a + b }, { a, b -> a * b }))
+
+    override fun partTwo() = equations.calibrationResult(setOf({ a, b -> a + b }, { a, b -> a * b }, { a, b -> "$a$b".toLong() }))
 
+    companion object {
+        private fun List<Pair<Long, List<Long>>>.calibrationResult(operators: Set<(Long, Long) -> Long>) =
+            filter { (result, numbers) ->
                 val results =
                     numbers
                         .drop(1)
                         .fold(setOf(numbers.first())) { candidates, number ->
-                            candidates.flatMap { candidate -> setOf(candidate + number, candidate * number) }.toSet()
+                            candidates.flatMap { candidate -> operators.map { operator -> operator(candidate, number) } }.toSet()
                         }
 
-                if (result in results) result else null
+                result in results
             }
-            .sum()
+                .sumOf { (result, _) -> result }
+    }
 }
diff --git a/src/test/kotlin/adventofcode/year2024/Day07BridgeRepairSpec.kt b/src/test/kotlin/adventofcode/year2024/Day07BridgeRepairSpec.kt
@@ -2,4 +2,4 @@ package adventofcode.year2024
 
 import adventofcode.PuzzleBaseSpec
 
-class Day07BridgeRepairSpec : PuzzleBaseSpec(3749)
+class Day07BridgeRepairSpec : PuzzleBaseSpec(3749, 11387)
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2,4 +2,4 @@ package adventofcode.year2024

		import adventofcode.PuzzleBaseSpec

		class Day07BridgeRepairSpec : PuzzleBaseSpec(3749)
		class Day07BridgeRepairSpec : PuzzleBaseSpec(3749, 11387)