day 19, part 1

AdventOfCode2020.xcodeproj/project.pbxproj

@@ -23,6 +23,9 @@
 		26BD88A5258C818300E92A8E /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26BD88A4258C818300E92A8E /* main.swift */; };
 		26BD88BB258C818E00E92A8E /* LoadData.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2AD3A2581713A00702405 /* LoadData.swift */; };
 		26BD88BC258C818E00E92A8E /* Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2ACE5257ED09000702405 /* Extensions.swift */; };
+		26DD9C41258DEAC70082D4F2 /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26DD9C40258DEAC70082D4F2 /* main.swift */; };
+		26DD9C58258DEACF0082D4F2 /* LoadData.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2AD3A2581713A00702405 /* LoadData.swift */; };
+		26DD9C59258DEACF0082D4F2 /* Extensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26E2ACE5257ED09000702405 /* Extensions.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 */; };
@@ -154,6 +157,15 @@
 			);
 			runOnlyForDeploymentPostprocessing = 1;
 		};
+		26DD9C3C258DEAC70082D4F2 /* CopyFiles */ = {
+			isa = PBXCopyFilesBuildPhase;
+			buildActionMask = 2147483647;
+			dstPath = /usr/share/man/man1/;
+			dstSubfolderSpec = 0;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 1;
+		};
 		26E2ACD3257ECFFA00702405 /* CopyFiles */ = {
 			isa = PBXCopyFilesBuildPhase;
 			buildActionMask = 2147483647;
@@ -249,6 +261,8 @@
 		26BD8864258B2D5300E92A8E /* main.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = main.swift; sourceTree = "<group>"; };
 		26BD88A2258C818300E92A8E /* day18 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = day18; sourceTree = BUILT_PRODUCTS_DIR; };
 		26BD88A4258C818300E92A8E /* main.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = main.swift; sourceTree = "<group>"; };
+		26DD9C3E258DEAC70082D4F2 /* day19 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = day19; sourceTree = BUILT_PRODUCTS_DIR; };
+		26DD9C40258DEAC70082D4F2 /* 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>"; };
@@ -340,6 +354,13 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
+		26DD9C3B258DEAC70082D4F2 /* Frameworks */ = {
+			isa = PBXFrameworksBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
 		26E2ACD2257ECFFA00702405 /* Frameworks */ = {
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
@@ -437,6 +458,7 @@
 				261C554625895FB70035FEC0 /* day16 */,
 				26BD8863258B2D5300E92A8E /* day17 */,
 				26BD88A3258C818300E92A8E /* day18 */,
+				26DD9C3F258DEAC70082D4F2 /* day19 */,
 				268D953A25781DD80030EC4D /* Products */,
 			);
 			sourceTree = "<group>";
@@ -462,6 +484,7 @@
 				261C554525895FB70035FEC0 /* day16 */,
 				26BD8862258B2D5300E92A8E /* day17 */,
 				26BD88A2258C818300E92A8E /* day18 */,
+				26DD9C3E258DEAC70082D4F2 /* day19 */,
 			);
 			name = Products;
 			sourceTree = "<group>";
@@ -530,6 +553,14 @@
 			path = day18;
 			sourceTree = "<group>";
 		};
+		26DD9C3F258DEAC70082D4F2 /* day19 */ = {
+			isa = PBXGroup;
+			children = (
+				26DD9C40258DEAC70082D4F2 /* main.swift */,
+			);
+			path = day19;
+			sourceTree = "<group>";
+		};
 		26E2ACD6257ECFFA00702405 /* day8 */ = {
 			isa = PBXGroup;
 			children = (
@@ -776,6 +807,23 @@
 			productReference = 26BD88A2258C818300E92A8E /* day18 */;
 			productType = "com.apple.product-type.tool";
 		};
+		26DD9C3D258DEAC70082D4F2 /* day19 */ = {
+			isa = PBXNativeTarget;
+			buildConfigurationList = 26DD9C44258DEAC70082D4F2 /* Build configuration list for PBXNativeTarget "day19" */;
+			buildPhases = (
+				26DD9C3A258DEAC70082D4F2 /* Sources */,
+				26DD9C3B258DEAC70082D4F2 /* Frameworks */,
+				26DD9C3C258DEAC70082D4F2 /* CopyFiles */,
+			);
+			buildRules = (
+			);
+			dependencies = (
+			);
+			name = day19;
+			productName = day19;
+			productReference = 26DD9C3E258DEAC70082D4F2 /* day19 */;
+			productType = "com.apple.product-type.tool";
+		};
 		26E2ACD4257ECFFA00702405 /* day8 */ = {
 			isa = PBXNativeTarget;
 			buildConfigurationList = 26E2ACDB257ECFFA00702405 /* Build configuration list for PBXNativeTarget "day8" */;
@@ -951,6 +999,9 @@
 					26BD88A1258C818300E92A8E = {
 						CreatedOnToolsVersion = 12.3;
 					};
+					26DD9C3D258DEAC70082D4F2 = {
+						CreatedOnToolsVersion = 12.3;
+					};
 					26E2ACD4257ECFFA00702405 = {
 						CreatedOnToolsVersion = 12.2;
 					};
@@ -1008,6 +1059,7 @@
 				261C554425895FB70035FEC0 /* day16 */,
 				26BD8861258B2D5300E92A8E /* day17 */,
 				26BD88A1258C818300E92A8E /* day18 */,
+				26DD9C3D258DEAC70082D4F2 /* day19 */,
 			);
 		};
 /* End PBXProject section */
@@ -1113,6 +1165,16 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
+		26DD9C3A258DEAC70082D4F2 /* Sources */ = {
+			isa = PBXSourcesBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+				26DD9C41258DEAC70082D4F2 /* main.swift in Sources */,
+				26DD9C59258DEACF0082D4F2 /* Extensions.swift in Sources */,
+				26DD9C58258DEACF0082D4F2 /* LoadData.swift in Sources */,
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
 		26E2ACD1257ECFFA00702405 /* Sources */ = {
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
@@ -1549,6 +1611,28 @@
 			};
 			name = Release;
 		};
+		26DD9C42258DEAC70082D4F2 /* Debug */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Automatic;
+				DEVELOPMENT_TEAM = 722B335UM5;
+				ENABLE_HARDENED_RUNTIME = YES;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Debug;
+		};
+		26DD9C43258DEAC70082D4F2 /* Release */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Automatic;
+				DEVELOPMENT_TEAM = 722B335UM5;
+				ENABLE_HARDENED_RUNTIME = YES;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Release;
+		};
 		26E2ACD9257ECFFA00702405 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
@@ -1843,6 +1927,15 @@
 			defaultConfigurationIsVisible = 0;
 			defaultConfigurationName = Release;
 		};
+		26DD9C44258DEAC70082D4F2 /* Build configuration list for PBXNativeTarget "day19" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				26DD9C42258DEAC70082D4F2 /* Debug */,
+				26DD9C43258DEAC70082D4F2 /* Release */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
 		26E2ACDB257ECFFA00702405 /* Build configuration list for PBXNativeTarget "day8" */ = {
 			isa = XCConfigurationList;
 			buildConfigurations = (

day19/main.swift

@@ -0,0 +1,142 @@
+import Foundation
+
+let input = loadData(day: 19)
+let scanner = Scanner(string: input)
+scanner.charactersToBeSkipped = .whitespaces
+
+enum Rule {
+    case character(Character)
+    indirect case sequence(Rule, Rule)
+    indirect case alternative(Rule, Rule)
+    case reference(Int)
+}
+
+
+typealias RuleSet = [Int: Rule]
+
+extension Scanner {
+    func parseRuleSet() -> RuleSet {
+        var result: [Int: Rule] = [:]
+        while !string("\n") {
+            guard let (index, rule) = parseRuleDefinition() else { fatalError() }
+            result[index] = rule
+        }
+
+        return result
+    }
+
+    func parseRuleDefinition() -> (Int, Rule)? {
+        guard let label = parseLabel(),
+              let rule = parseRule(),
+              string("\n")
+        else { return nil }
+        return (label, rule)
+    }
+
+    func parseLabel() -> Int? {
+        guard let num = scanInt(),
+              string(":")
+        else { return nil }
+        return num
+    }
+
+    func parseRule() -> Rule? {
+        if string("\""), let character = scanCharacter(), string("\"") {
+            return .character(character)
+        }
+
+        guard let sequence = parseSequence() else { return nil }
+
+        if string("|"), let rhs = parseSequence() {
+            return .alternative(sequence, rhs)
+        }
+
+        return sequence
+    }
+
+    func parseReference() -> Rule? {
+        guard let num = scanInt() else { return nil }
+        return .reference(num)
+    }
+
+    func parseSequence() -> Rule? {
+        guard var sequence = parseReference() else {
+            return nil
+        }
+
+        while let rhs = parseReference() {
+            sequence = .sequence(sequence, rhs)
+        }
+
+        return sequence
+    }
+}
+
+let rules = scanner.parseRuleSet()
+
+extension Rule {
+    func matches(rules: RuleSet, _ s: Substring) -> Substring? {
+        switch self {
+        case .character(let ch):
+            if s.first == ch {
+                return s.dropFirst()
+            }
+
+            return nil
+
+        case let .sequence(first, second):
+            if let firstMatch = first.matches(rules: rules, s), let secondMatch = second.matches(rules: rules, firstMatch) {
+                return secondMatch
+            }
+
+            return nil
+
+        case let .alternative(first, second):
+            if let firstMatch = first.matches(rules: rules, s) {
+                return firstMatch
+            }
+
+            if let secondMatch = second.matches(rules: rules, s) {
+                return secondMatch
+            }
+
+            return nil
+
+        case .reference(let index):
+            return rules[index]!.matches(rules: rules, s)
+        }
+    }
+
+    func matches(rules: RuleSet, _ s: String) -> Bool {
+        if let result = matches(rules: rules, s[...]), result.isEmpty {
+            return true
+        }
+
+        return false
+    }
+}
+
+extension Scanner {
+    func scanLine() -> String? {
+        guard let result = scanUpToCharacters(from: .newlines),
+              scanCharacters(from: .newlines) != nil else {
+            return nil
+        }
+        return result
+    }
+
+    func readLines() -> [String] {
+
+        var lines = [String]()
+        while let line = scanner.scanLine() {
+            lines.append(line)
+        }
+        return lines
+    }
+
+}
+
+let messages = scanner.readLines()
+
+print("part 1", messages.lazy.filter { rules[0]!.matches(rules: rules, $0) }.count)
+