[2024/7] Bridge Repair (Part 1)

pfolta · Dec 7, 2024 · a52ef94 · a52ef94
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diff --git a/README.md b/README.md
@@ -28,7 +28,7 @@
 |     2021 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |        |   ★    |   ★    |        |        |        |        |        |        |        |        |        |        |        |    26 |
 |     2022 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ★    |   ★    |   ★    |   ★    |        |        |        |        |        |        |        |   ☆    |        |        |        |   ☆    |    28 |
 |     2023 |   ★   |   ★   |   ★   |   ★   |   ☆   |   ★   |   ☆   |       |       |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |    12 |
-|     2024 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |       |       |       |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |    12 |
+|     2024 |   ★   |   ★   |   ★   |   ★   |   ★   |   ★   |   ☆   |       |       |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |        |    13 |
 
 ## 🛷 How to run
 
@@ -170,6 +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`        |                                                  |
 
 ## 🕯️ Useful commands
 

diff --git a/src/main/kotlin/adventofcode/year2024/Day07BridgeRepair.kt b/src/main/kotlin/adventofcode/year2024/Day07BridgeRepair.kt
@@ -0,0 +1,24 @@
+package adventofcode.year2024
+
+import adventofcode.Puzzle
+import adventofcode.PuzzleInput
+
+class Day07BridgeRepair(customInput: PuzzleInput? = null) : Puzzle(customInput) {
+    override fun partOne() =
+        input
+            .lines()
+            .mapNotNull { equation ->
+                val result = equation.split(": ").first().toLong()
+                val numbers = equation.split(": ").last().split(" ").map(String::toLong)
+
+                val results =
+                    numbers
+                        .drop(1)
+                        .fold(setOf(numbers.first())) { candidates, number ->
+                            candidates.flatMap { candidate -> setOf(candidate + number, candidate * number) }.toSet()
+                        }
+
+                if (result in results) result else null
+            }
+            .sum()
+}