Add 2023, day 10, part 1

Advent/Sources/Conversion/RawRepresentable.swift

@@ -20,5 +20,5 @@ public struct UnexpectedRawValue<RawValue>: Error {
 
 extension UnexpectedRawValue: CustomStringConvertible {
 
-    public var description: String { #"Unexpected rawValue: "\(rawValue)"."# }
+    public var description: String { #"Unexpected rawValue: "\#(rawValue)"."# }
 }

Year2023/Sources/Day10.swift

@@ -0,0 +1,62 @@
+
+import Advent
+import Algorithms
+import Foundation
+
+public enum Day10: Day {
+
+    public static let title = "Pipe Maze"
+
+    public static func part1(_ input: Input) throws -> Int {
+
+        let grid = try Grid<Position2D<Int>, Tile>(rawValues: input.lines.reversed())
+        var current = try [grid.firstPosition(of: .start).unwrapped]
+        var covered: Set<Position2D<Int>> = []
+        var steps = 0
+
+        while Set(current).count == current.count {
+            covered.formUnion(current)
+            steps += 1
+            current = current.flatMap { position -> [Position2D<Int>] in
+                guard let tile = grid[position] else { return [] }
+                return tile
+                    .neighbours
+                    .map { position + $0 }
+                    .filter { !covered.contains($0) }
+                    .filter { next in // Ensure next pipe leads back to us.
+                        guard let tile = grid[next] else { return false}
+                        return tile.neighbours.map { next + $0 }.contains(position)
+                    }
+            }
+        }
+
+        return steps
+    }
+
+    public static func part2(_ input: Input) throws -> Int {
+        0
+    }
+}
+
+private struct Tile: RawRepresentable, Equatable {
+
+    static let start = try! Self("S")
+
+    let rawValue: Character
+    let neighbours: [Vector2D<Int>]
+
+    init?(rawValue: Character) {
+        self.rawValue = rawValue
+        switch rawValue {
+        case "|": neighbours = [.north, .south]
+        case "-": neighbours = [.east, .west]
+        case "L": neighbours = [.north, .east]
+        case "J": neighbours = [.north, .west]
+        case "7": neighbours = [.south, .west]
+        case "F": neighbours = [.south, .east]
+        case ".": neighbours = []
+        case "S": neighbours = Vector2D<Int>.orthogonal
+        default: return nil
+        }
+    }
+}

Year2023/Tests/Day10Tests.swift

@@ -0,0 +1,51 @@
+
+import Advent
+import Year2023
+import XCTest
+
+final class Day10Tests: XCTestCase {
+
+    func testPart1Example1() throws {
+        XCTAssertEqual(try Day10.part1([
+            ".....",
+            ".S-7.",
+            ".|.|.",
+            ".L-J.",
+            ".....",
+        ]), 4)
+    }
+
+    func testPart1Example2() throws {
+        XCTAssertEqual(try Day10.part1([
+            "..F7.",
+            ".FJ|.",
+            "SJ.L7",
+            "|F--J",
+            "LJ...",
+        ]), 8)
+    }
+
+    func testPart1Example3() throws {
+        XCTAssertEqual(try Day10.part1([
+            "7-F7-",
+            ".FJ|7",
+            "SJLL7",
+            "|F--J",
+            "LJ.LJ",
+        ]), 8)
+    }
+
+    func testPart1Puzzle() throws {
+        let input = try Bundle.module.input(named: "Day10")
+        XCTAssertEqual(try Day10.part1(input), 7063)
+    }
+
+    func testPart2Examples() throws {
+        XCTAssertEqual(try Day10.part2([]), 0)
+    }
+
+    func testPart2Puzzle() throws {
+        let input = try Bundle.module.input(named: "Day10")
+        XCTAssertEqual(try Day10.part2(input), 0)
+    }
+}