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2020/day17/main.swift

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+import Foundation
+
+let input = loadData(day: 17).lines()
+
+struct Coordinate: Hashable {
+    var x, y, z, w: Int
+}
+
+
+
+struct Cube {
+    var cube: [Coordinate: Bool] = [:]
+    var minX = 0
+    var maxX = 0
+    var minY = 0
+    var maxY = 0
+    var minZ = 0
+    var maxZ = 0
+    var minW = 0
+    var maxW = 0
+
+    func neighbors(_ c: Coordinate) -> Int {
+        var count = 0
+        for xOffset in -1...1 {
+            for yOffset in -1...1 {
+                for zOffset in -1...1 {
+                    for wOffset in -1 ... 1 {
+                        guard !(xOffset == 0 && yOffset == 0 && zOffset == 0 && wOffset == 0) else { continue }
+                        let current = Coordinate(x: c.x + xOffset, y: c.y + yOffset, z: c.z + zOffset, w: c.w + wOffset)
+                        if let value = cube[current], value {
+                            count += 1
+                        }
+                    }
+                }
+            }
+        }
+        return count
+    }
+
+    subscript(_ x: Int, _ y : Int, _ z : Int, _ w : Int ) -> Bool {
+        get {
+            cube[Coordinate(x: x, y: y, z: z, w: w)] ?? false
+        }
+
+        set {
+            cube[Coordinate(x: x, y: y, z: z, w: w)] = newValue
+            if newValue {
+                minX = min(x, minX)
+                minY = min(y, minY)
+                minZ = min(z, minZ)
+                maxX = max(x, maxX)
+                maxY = max(y, maxY)
+                maxZ = max(z, maxZ)
+                minW = min(w, minW)
+                maxW = max(w, maxW)
+            }
+        }
+    }
+
+}
+
+var cube = Cube()
+
+func cycle() -> Cube {
+    var result = cube
+
+    for x in cube.minX - 1 ... cube.maxX + 1 {
+        for y in cube.minY - 1 ... cube.maxY + 1 {
+            for z in cube.minZ - 1 ... cube.maxZ + 1 {
+                for w in cube.minW - 1 ... cube.maxW + 1 {
+                    let n = cube.neighbors(Coordinate(x: x, y: y, z: z, w: w))
+                    if cube[x, y, z, w] {
+                        if n < 2 || n > 3 {
+                            result[x, y, z, w] = false
+                        }
+                    } else {
+                        if n == 3 {
+                            result[x, y, z, w] = true
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    return result
+}
+
+
+for (y, line) in input.enumerated() {
+    for (x, char) in line.enumerated() {
+        cube[x, y, 0, 0] = char == "#"
+    }
+}
+
+for _ in 0..<6 {
+    cube = cycle()
+}
+
+print(cube.cube.values.reduce(0, { $0 + ($1 ? 1 : 0) }))