Day 16

AdventOfCode2020.xcodeproj/project.pbxproj

@@ -8,6 +8,9 @@
 
 /* Begin PBXBuildFile section */
 		26176242257DFD0800D00A66 /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26176241257DFD0800D00A66 /* main.swift */; };
+		261C554825895FB70035FEC0 /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = 261C554725895FB70035FEC0 /* main.swift */; };
+		261C555C25895FBF0035FEC0 /* LoadData.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2AD3A2581713A00702405 /* LoadData.swift */; };
+		261C555D25895FBF0035FEC0 /* Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2ACE5257ED09000702405 /* Extensions.swift */; };
 		268D953D25781DD80030EC4D /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = 268D953C25781DD80030EC4D /* main.swift */; };
 		268D954B25781F740030EC4D /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = 268D954A25781F740030EC4D /* main.swift */; };
 		268D955C257904250030EC4D /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = 268D955B257904250030EC4D /* main.swift */; };
@@ -64,6 +67,15 @@
 			);
 			runOnlyForDeploymentPostprocessing = 1;
 		};
+		261C554325895FB70035FEC0 /* CopyFiles */ = {
+			isa = PBXCopyFilesBuildPhase;
+			buildActionMask = 2147483647;
+			dstPath = /usr/share/man/man1/;
+			dstSubfolderSpec = 0;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 1;
+		};
 		268D953725781DD80030EC4D /* CopyFiles */ = {
 			isa = PBXCopyFilesBuildPhase;
 			buildActionMask = 2147483647;
@@ -195,6 +207,8 @@
 /* Begin PBXFileReference section */
 		2617623F257DFD0800D00A66 /* day7 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = day7; sourceTree = BUILT_PRODUCTS_DIR; };
 		26176241257DFD0800D00A66 /* main.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = main.swift; sourceTree = "<group>"; };
+		261C554525895FB70035FEC0 /* day16 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = day16; sourceTree = BUILT_PRODUCTS_DIR; };
+		261C554725895FB70035FEC0 /* main.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = main.swift; sourceTree = "<group>"; };
 		268D953925781DD80030EC4D /* day1 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = day1; sourceTree = BUILT_PRODUCTS_DIR; };
 		268D953C25781DD80030EC4D /* main.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = main.swift; sourceTree = "<group>"; };
 		268D954825781F740030EC4D /* day2 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = day2; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -235,6 +249,13 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
+		261C554225895FB70035FEC0 /* Frameworks */ = {
+			isa = PBXFrameworksBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
 		268D953625781DD80030EC4D /* Frameworks */ = {
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
@@ -344,6 +365,14 @@
 			path = day7;
 			sourceTree = "<group>";
 		};
+		261C554625895FB70035FEC0 /* day16 */ = {
+			isa = PBXGroup;
+			children = (
+				261C554725895FB70035FEC0 /* main.swift */,
+			);
+			path = day16;
+			sourceTree = "<group>";
+		};
 		268D953025781DD80030EC4D = {
 			isa = PBXGroup;
 			children = (
@@ -363,6 +392,7 @@
 				26E2ADAA2586024700702405 /* day13 */,
 				26E2ADE225873BBE00702405 /* day14 */,
 				26E2AE0B2587E07A00702405 /* day15 */,
+				261C554625895FB70035FEC0 /* day16 */,
 				268D953A25781DD80030EC4D /* Products */,
 			);
 			sourceTree = "<group>";
@@ -385,6 +415,7 @@
 				26E2ADA92586024700702405 /* day13 */,
 				26E2ADE125873BBD00702405 /* day14 */,
 				26E2AE0A2587E07A00702405 /* day15 */,
+				261C554525895FB70035FEC0 /* day16 */,
 			);
 			name = Products;
 			sourceTree = "<group>";
@@ -530,6 +561,23 @@
 			productReference = 2617623F257DFD0800D00A66 /* day7 */;
 			productType = "com.apple.product-type.tool";
 		};
+		261C554425895FB70035FEC0 /* day16 */ = {
+			isa = PBXNativeTarget;
+			buildConfigurationList = 261C554B25895FB70035FEC0 /* Build configuration list for PBXNativeTarget "day16" */;
+			buildPhases = (
+				261C554125895FB70035FEC0 /* Sources */,
+				261C554225895FB70035FEC0 /* Frameworks */,
+				261C554325895FB70035FEC0 /* CopyFiles */,
+			);
+			buildRules = (
+			);
+			dependencies = (
+			);
+			name = day16;
+			productName = day16;
+			productReference = 261C554525895FB70035FEC0 /* day16 */;
+			productType = "com.apple.product-type.tool";
+		};
 		268D953825781DD80030EC4D /* day1 */ = {
 			isa = PBXNativeTarget;
 			buildConfigurationList = 268D954025781DD80030EC4D /* Build configuration list for PBXNativeTarget "day1" */;
@@ -780,6 +828,9 @@
 					2617623E257DFD0800D00A66 = {
 						CreatedOnToolsVersion = 12.2;
 					};
+					261C554425895FB70035FEC0 = {
+						CreatedOnToolsVersion = 12.2;
+					};
 					268D953825781DD80030EC4D = {
 						CreatedOnToolsVersion = 12.2;
 					};
@@ -852,6 +903,7 @@
 				26E2ADA82586024700702405 /* day13 */,
 				26E2ADE025873BBD00702405 /* day14 */,
 				26E2AE092587E07A00702405 /* day15 */,
+				261C554425895FB70035FEC0 /* day16 */,
 			);
 		};
 /* End PBXProject section */
@@ -867,6 +919,16 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
+		261C554125895FB70035FEC0 /* Sources */ = {
+			isa = PBXSourcesBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+				261C554825895FB70035FEC0 /* main.swift in Sources */,
+				261C555D25895FBF0035FEC0 /* Extensions.swift in Sources */,
+				261C555C25895FBF0035FEC0 /* LoadData.swift in Sources */,
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
 		268D953525781DD80030EC4D /* Sources */ = {
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
@@ -1032,6 +1094,28 @@
 			};
 			name = Release;
 		};
+		261C554925895FB70035FEC0 /* Debug */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Automatic;
+				DEVELOPMENT_TEAM = 722B335UM5;
+				ENABLE_HARDENED_RUNTIME = YES;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Debug;
+		};
+		261C554A25895FB70035FEC0 /* Release */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Automatic;
+				DEVELOPMENT_TEAM = 722B335UM5;
+				ENABLE_HARDENED_RUNTIME = YES;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Release;
+		};
 		268D953E25781DD80030EC4D /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
@@ -1467,6 +1551,15 @@
 			defaultConfigurationIsVisible = 0;
 			defaultConfigurationName = Release;
 		};
+		261C554B25895FB70035FEC0 /* Build configuration list for PBXNativeTarget "day16" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				261C554925895FB70035FEC0 /* Debug */,
+				261C554A25895FB70035FEC0 /* Release */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
 		268D953425781DD80030EC4D /* Build configuration list for PBXProject "AdventOfCode2020" */ = {
 			isa = XCConfigurationList;
 			buildConfigurations = (

common/Extensions.swift

@@ -31,3 +31,9 @@ extension Sequence {
         return self
     }
 }
+
+extension Collection where Element: Collection {
+    func flatten() -> [Element.Element] {
+        flatMap { $0 }
+    }
+}

day16/main.swift

@@ -0,0 +1,116 @@
+import Foundation
+
+let input = loadData(day: 16)
+let scanner = Scanner(string: input)
+
+extension Scanner {
+    func scanRange() -> ClosedRange<Int>? {
+        guard let low = scanInt(),
+              string("-"),
+              let high = scanInt()
+        else { return nil }
+        return low...high
+    }
+
+    func scanFieldDefinition() -> (String, ClosedRange<Int>, ClosedRange<Int>)? {
+        var location = scanLocation
+        guard let name = scanUpToString(":"),
+              string(":"),
+              let first = scanRange(),
+              string("or"),
+              let second = scanRange()
+        else {
+            scanLocation = location
+            return nil
+        }
+        return (name, first, second)
+    }
+
+    func scanFieldDefinitions() -> [(String, ClosedRange<Int>, ClosedRange<Int>)] {
+        var result = [(String, ClosedRange<Int>, ClosedRange<Int>)]()
+        while let field = scanFieldDefinition() {
+            result.append(field)
+        }
+
+        return result
+    }
+
+    func scanTicket() -> [Int]? {
+        var result = [Int]()
+        repeat {
+            guard let field = scanInt() else { return nil }
+            result.append(field)
+        } while string(",")
+        return result
+    }
+
+    func scanYourTicket() -> [Int]? {
+        guard string("your ticket:"),
+              let ticket = scanTicket()
+        else { return nil }
+        return ticket
+    }
+
+    func scanNearbyTickets() -> [[Int]]? {
+        guard string("nearby tickets:") else { return nil }
+        var result = [[Int]]()
+        while !isAtEnd {
+            guard let ticket = scanTicket() else { return nil }
+            result.append(ticket)
+        }
+        return result
+    }
+}
+
+let definitions = scanner.scanFieldDefinitions()
+guard let yourTicket = scanner.scanYourTicket(),
+      let nearbyTickets = scanner.scanNearbyTickets()
+else { fatalError() }
+
+
+func isValid(_ value: Int) -> Bool {
+    definitions.contains {
+        $0.1.contains(value) || $0.2.contains(value)
+    }
+}
+
+func isValid(_ ticket: [Int]) -> Bool {
+    ticket.allSatisfy(isValid)
+}
+
+let invalidSums = nearbyTickets
+    .flatten()
+    .filter( { !isValid($0) } )
+    .reduce(0, +)
+
+print(invalidSums)
+
+
+var possibleFields: [Set<String>] = Array(repeating: Set(definitions.map { $0.0 }), count: yourTicket.count)
+
+for ticket in nearbyTickets where isValid(ticket) {
+    for (index, value) in ticket.enumerated() {
+        for (name, first, second) in definitions {
+            if !(first.contains(value) || second.contains(value)) {
+                possibleFields[index].remove(name)
+            }
+        }
+    }
+}
+
+for index in possibleFields.indices.sorted(by: { possibleFields[$0].count < possibleFields[$1].count }) {
+    guard possibleFields[index].count == 1, let key = possibleFields[index].first else { fatalError() }
+    for i in possibleFields.indices where i != index {
+        possibleFields[i].remove(key)
+    }
+}
+
+let mapping = possibleFields.map { $0.first! }
+
+let result = mapping.enumerated()
+    .map { ($0.element, yourTicket[$0.offset]) }
+    .filter { $0.0.hasPrefix("departure") }
+    .map { $0.1 }
+    .reduce(1, *)
+
+print(result)