Day 24 Part 1 + 2

AdventOfCode2020.xcodeproj/project.pbxproj

@@ -38,6 +38,9 @@
 		26DD9D2E259312410082D4F2 /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26DD9D2D259312410082D4F2 /* main.swift */; };
 		26DD9D49259312460082D4F2 /* Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2ACE5257ED09000702405 /* Extensions.swift */; };
 		26DD9D4A259312460082D4F2 /* LoadData.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2AD3A2581713A00702405 /* LoadData.swift */; };
+		26DD9DDC25949F600082D4F2 /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26DD9DDB25949F600082D4F2 /* main.swift */; };
+		26DD9DF825949F690082D4F2 /* Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2ACE5257ED09000702405 /* Extensions.swift */; };
+		26DD9DF925949F690082D4F2 /* LoadData.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2AD3A2581713A00702405 /* LoadData.swift */; };
 		26E2ACD8257ECFFA00702405 /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2ACD7257ECFFA00702405 /* main.swift */; };
 		26E2ACE6257ED09000702405 /* Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2ACE5257ED09000702405 /* Extensions.swift */; };
 		26E2ACE7257ED09000702405 /* Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2ACE5257ED09000702405 /* Extensions.swift */; };
@@ -214,6 +217,15 @@
 			);
 			runOnlyForDeploymentPostprocessing = 1;
 		};
+		26DD9DD725949F600082D4F2 /* CopyFiles */ = {
+			isa = PBXCopyFilesBuildPhase;
+			buildActionMask = 2147483647;
+			dstPath = /usr/share/man/man1/;
+			dstSubfolderSpec = 0;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 1;
+		};
 		26E2ACD3257ECFFA00702405 /* CopyFiles */ = {
 			isa = PBXCopyFilesBuildPhase;
 			buildActionMask = 2147483647;
@@ -319,6 +331,8 @@
 		26DD9CF42591C4000082D4F2 /* main.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = main.swift; sourceTree = "<group>"; };
 		26DD9D2B259312410082D4F2 /* day23 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = day23; sourceTree = BUILT_PRODUCTS_DIR; };
 		26DD9D2D259312410082D4F2 /* main.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = main.swift; sourceTree = "<group>"; };
+		26DD9DD925949F600082D4F2 /* day24 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = day24; sourceTree = BUILT_PRODUCTS_DIR; };
+		26DD9DDB25949F600082D4F2 /* main.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = main.swift; sourceTree = "<group>"; };
 		26E2ACD5257ECFFA00702405 /* day8 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = day8; sourceTree = BUILT_PRODUCTS_DIR; };
 		26E2ACD7257ECFFA00702405 /* main.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = main.swift; sourceTree = "<group>"; };
 		26E2ACE5257ED09000702405 /* Extensions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Extensions.swift; sourceTree = "<group>"; };
@@ -445,6 +459,13 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
+		26DD9DD625949F600082D4F2 /* Frameworks */ = {
+			isa = PBXFrameworksBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
 		26E2ACD2257ECFFA00702405 /* Frameworks */ = {
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
@@ -547,6 +568,7 @@
 				26DD9CA72590759B0082D4F2 /* day21 */,
 				26DD9CF32591C4000082D4F2 /* day22 */,
 				26DD9D2C259312410082D4F2 /* day23 */,
+				26DD9DDA25949F600082D4F2 /* day24 */,
 				268D953A25781DD80030EC4D /* Products */,
 			);
 			sourceTree = "<group>";
@@ -577,6 +599,7 @@
 				26DD9CA62590759B0082D4F2 /* day21 */,
 				26DD9CF22591C4000082D4F2 /* day22 */,
 				26DD9D2B259312410082D4F2 /* day23 */,
+				26DD9DD925949F600082D4F2 /* day24 */,
 			);
 			name = Products;
 			sourceTree = "<group>";
@@ -685,6 +708,14 @@
 			path = day23;
 			sourceTree = "<group>";
 		};
+		26DD9DDA25949F600082D4F2 /* day24 */ = {
+			isa = PBXGroup;
+			children = (
+				26DD9DDB25949F600082D4F2 /* main.swift */,
+			);
+			path = day24;
+			sourceTree = "<group>";
+		};
 		26E2ACD6257ECFFA00702405 /* day8 */ = {
 			isa = PBXGroup;
 			children = (
@@ -1016,6 +1047,23 @@
 			productReference = 26DD9D2B259312410082D4F2 /* day23 */;
 			productType = "com.apple.product-type.tool";
 		};
+		26DD9DD825949F600082D4F2 /* day24 */ = {
+			isa = PBXNativeTarget;
+			buildConfigurationList = 26DD9DDF25949F600082D4F2 /* Build configuration list for PBXNativeTarget "day24" */;
+			buildPhases = (
+				26DD9DD525949F600082D4F2 /* Sources */,
+				26DD9DD625949F600082D4F2 /* Frameworks */,
+				26DD9DD725949F600082D4F2 /* CopyFiles */,
+			);
+			buildRules = (
+			);
+			dependencies = (
+			);
+			name = day24;
+			productName = day24;
+			productReference = 26DD9DD925949F600082D4F2 /* day24 */;
+			productType = "com.apple.product-type.tool";
+		};
 		26E2ACD4257ECFFA00702405 /* day8 */ = {
 			isa = PBXNativeTarget;
 			buildConfigurationList = 26E2ACDB257ECFFA00702405 /* Build configuration list for PBXNativeTarget "day8" */;
@@ -1206,6 +1254,9 @@
 					26DD9D2A259312410082D4F2 = {
 						CreatedOnToolsVersion = 12.3;
 					};
+					26DD9DD825949F600082D4F2 = {
+						CreatedOnToolsVersion = 12.3;
+					};
 					26E2ACD4257ECFFA00702405 = {
 						CreatedOnToolsVersion = 12.2;
 					};
@@ -1268,6 +1319,7 @@
 				26DD9CA52590759B0082D4F2 /* day21 */,
 				26DD9CF12591C4000082D4F2 /* day22 */,
 				26DD9D2A259312410082D4F2 /* day23 */,
+				26DD9DD825949F600082D4F2 /* day24 */,
 			);
 		};
 /* End PBXProject section */
@@ -1423,6 +1475,16 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
+		26DD9DD525949F600082D4F2 /* Sources */ = {
+			isa = PBXSourcesBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+				26DD9DDC25949F600082D4F2 /* main.swift in Sources */,
+				26DD9DF825949F690082D4F2 /* Extensions.swift in Sources */,
+				26DD9DF925949F690082D4F2 /* LoadData.swift in Sources */,
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
 		26E2ACD1257ECFFA00702405 /* Sources */ = {
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
@@ -1969,6 +2031,28 @@
 			};
 			name = Release;
 		};
+		26DD9DDD25949F600082D4F2 /* Debug */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Automatic;
+				DEVELOPMENT_TEAM = 722B335UM5;
+				ENABLE_HARDENED_RUNTIME = YES;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Debug;
+		};
+		26DD9DDE25949F600082D4F2 /* Release */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Automatic;
+				DEVELOPMENT_TEAM = 722B335UM5;
+				ENABLE_HARDENED_RUNTIME = YES;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Release;
+		};
 		26E2ACD9257ECFFA00702405 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
@@ -2308,6 +2392,15 @@
 			defaultConfigurationIsVisible = 0;
 			defaultConfigurationName = Release;
 		};
+		26DD9DDF25949F600082D4F2 /* Build configuration list for PBXNativeTarget "day24" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				26DD9DDD25949F600082D4F2 /* Debug */,
+				26DD9DDE25949F600082D4F2 /* Release */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
 		26E2ACDB257ECFFA00702405 /* Build configuration list for PBXNativeTarget "day8" */ = {
 			isa = XCConfigurationList;
 			buildConfigurations = (

day24/main.swift

@@ -0,0 +1,129 @@
+import Foundation
+
+let input = loadData(day: 24)
+let scanner = Scanner(string: input)
+scanner.charactersToBeSkipped = nil
+
+enum Direction: String, CaseIterable {
+    case east = "e"
+    case southEast = "se"
+    case southWest = "sw"
+    case west = "w"
+    case northWest = "nw"
+    case northEast = "ne"
+}
+
+extension Scanner {
+    func readDirection() -> Direction? {
+        for dir in Direction.allCases {
+            if string(dir.rawValue) {
+                return dir
+            }
+        }
+        return nil
+    }
+}
+
+struct Coord: Hashable {
+    var south: Int
+    var east: Int
+
+    static let zero = Coord(south: 0, east: 0)
+
+    mutating func move(_ direction: Direction) {
+        switch direction {
+        case .east:
+            east += 1
+        case .southEast:
+            south += 1
+
+        case  .southWest:
+            south += 1
+            east -= 1
+
+        case .west:
+            east -= 1
+
+        case .northWest:
+            south -= 1
+
+        case .northEast:
+            south -= 1
+            east += 1
+        }
+    }
+
+    func neighbor(_ direction: Direction) -> Coord {
+        var result = self
+        result.move(direction)
+        return result
+    }
+
+    var neighbors: [Coord] {
+        Direction.allCases.map(neighbor)
+    }
+}
+
+func readCoordinate() -> Coord {
+    var current = Coord.zero
+    while let direction = scanner.readDirection() {
+        current.move(direction)
+    }
+    precondition(scanner.string("\n"))
+    return current
+}
+
+var floor: [Coord: Bool] = [:]
+var northWestCorner = Coord.zero
+var southEastCorner = Coord.zero
+
+
+func expandRange(toInclude coord: Coord) {
+    northWestCorner.east = min(northWestCorner.east, coord.east)
+    northWestCorner.south = min(northWestCorner.south, coord.south)
+
+    southEastCorner.east = max(southEastCorner.east, coord.east)
+    southEastCorner.south = max(southEastCorner.south, coord.south)
+}
+
+while !scanner.isAtEnd {
+    let coord = readCoordinate()
+    expandRange(toInclude: coord)
+
+    floor[coord, default: false].toggle()
+}
+
+print("part 1:", floor.values.lazy.filter { $0 }.count)
+
+func step() -> [Coord: Bool] {
+    var result = floor
+
+    for east in (northWestCorner.east - 1)...(southEastCorner.east + 1) {
+        for south in (northWestCorner.south - 1)...(southEastCorner.south + 1) {
+            let coord = Coord(south: south, east: east)
+
+            let isBlack = floor[coord, default: false]
+
+            let blackNeighbors = coord.neighbors
+                .lazy
+                .map { floor[$0, default: false] }
+                .filter { $0 }
+                .count
+
+            if isBlack && (blackNeighbors == 0 || blackNeighbors > 2) {
+                result[coord] = false
+            } else if !isBlack && blackNeighbors == 2 {
+                result[coord] = true
+                expandRange(toInclude: coord)
+            }
+        }
+    }
+
+    return result
+}
+
+for _ in 0..<100 {
+    floor = step()
+}
+
+print("part 2:", floor.values.lazy.filter { $0 }.count)