Sources/09/09.swift

@@ -9,7 +9,7 @@ import Foundation
 import Runner
 import Collections
 
-struct Coord: Hashable {
+struct Coord {
     let row: Int
     let col: Int
     
@@ -33,34 +33,31 @@ struct Coord: Hashable {
 }
 
 struct Field:Sequence, IteratorProtocol {
-    typealias Element = Coord
     let numbers: [[Int]]
     let numCols: Int
     let numRows: Int
     
-    var neighbors = [Coord:[Coord]]()
-    
     var current: Coord? = Coord(row: 0, col: 0)
     
     init(numbers: [[Int]]) {
         self.numbers = numbers
-        numCols = numbers.first?.count ?? 0
+        numCols = numbers.first!.count
         numRows = numbers.count
     }
     
-    mutating func getNeighborsCoordsFor(coord: Coord) -> [Coord] {
-        let n = neighbors[coord] ?? [coord.getAbove(), coord.getRight(), coord.getBelow(), coord.getLeft()]
+    func getNeighborsCoordsFor(coord: Coord) -> [Coord] {
+        return [coord.getAbove(), coord.getRight(), coord.getBelow(), coord.getLeft()]
             .compactMap { $0 }
             .filter { $0.row < numRows && $0.col < numCols }
-        neighbors[coord] = n
-        return n
     }
     
-    mutating func isLowPointAt(coord: Coord) -> Bool {
-        let value = self[coord]
+    func lowPointValueAt(coord: Coord) -> Int? {
+        let value = numbers[coord.row][coord.col]
         return getNeighborsCoordsFor(coord: coord)
             .map { numbers[$0.row][$0.col] }
             .allSatisfy { $0 > value }
+        ? value
+        : nil
     }
     
     private func getNextCoord() -> Coord? {
@@ -82,59 +79,19 @@ struct Field:Sequence, IteratorProtocol {
         }
         return current
     }
-    
-    subscript(index: Coord) -> Int {
-        get {
-            numbers[index.row][index.col]
-        }/*
-        set(newValue) {
-            // Perform a suitable setting action here.
-        }*/
-    }
 }
 
-class  Day09: Runnable {
+struct Day09: Runnable {
     let inputPath: String
-    var lowestNeighbors = [Coord: Coord]()
-    var lowPoints = Set<Coord>()
-    var field = Field(numbers: [[Int]]())
     
-    required init(inputPath: String) {
-        self.inputPath = inputPath
-    }
-    
-    public func run() {
+    func run() {
         let input = try! String(contentsOfFile: inputPath)
         let entries = input
             .trimmingCharacters(in: .newlines)
             .components(separatedBy: .newlines)
             .map { line in line.map { $0.wholeNumberValue! } }
-        field = Field(numbers: entries)
-        lowPoints = Set(field.filter { field.isLowPointAt(coord: $0) })
-        
-        //Part 1
-        let sum = lowPoints.map { field[$0] }.reduce(0, +) + lowPoints.count
+        let field = Field(numbers: entries)
+        let sum = field.compactMap { field.lowPointValueAt(coord: $0) }.reduce(0, { $0 + $1 + 1 })
         print(sum)
-        
-        // Part 2:
-        var basinSize = [Coord: Int]()
-        for coord in field {
-            guard field[coord] != 9 else {
-                continue
-            }
-            let bl = basinLocation(for: coord)
-            basinSize[bl, default: 0] += 1
-        }
-        let result = basinSize.values.sorted(by: >)[0..<3].reduce(1, *)
-        print(result)
-    }
-    
-    private func basinLocation(for coord: Coord) -> Coord {
-        guard !lowPoints.contains(coord) else {
-            return coord
-        }
-        let closestNeighbor = lowestNeighbors[coord] ?? field.getNeighborsCoordsFor(coord: coord).min(by: { field[$0] < field[$1] })!
-        lowestNeighbors[coord] = closestNeighbor
-        return basinLocation(for: closestNeighbor)
     }
 }

Sources/09/main.swift

@@ -8,5 +8,5 @@
 import Foundation
 import Runner
 
-//Runner(target: Day09.self, day: "09", isTest: true).run()
-Runner(target: Day09.self, day: "09", isTest: false).run()
+Runner(target: Day09.self, day: "09", isTest: true).run()
+//Runner(target: Day09.self, day: "09", isTest: false).run()