Day 18

AoC21.xcodeproj/project.pbxproj

@@ -21,6 +21,8 @@
 		263CCF79276606730061B353 /* common.swift in Sources */ = {isa = PBXBuildFile; fileRef = 269BE5CB2762A08800871C85 /* common.swift */; };
 		263D3E33276DDA6600B0AC5B /* day17.swift in Sources */ = {isa = PBXBuildFile; fileRef = 263D3E32276DDA6600B0AC5B /* day17.swift */; };
 		263D3E34276DDA7000B0AC5B /* common.swift in Sources */ = {isa = PBXBuildFile; fileRef = 269BE5CB2762A08800871C85 /* common.swift */; };
+		263D3E40276E10A500B0AC5B /* common.swift in Sources */ = {isa = PBXBuildFile; fileRef = 269BE5CB2762A08800871C85 /* common.swift */; };
+		263D3E42276E10AE00B0AC5B /* day18.swift in Sources */ = {isa = PBXBuildFile; fileRef = 263D3E41276E10AE00B0AC5B /* day18.swift */; };
 		265112972767D16D009B7607 /* day13.swift in Sources */ = {isa = PBXBuildFile; fileRef = 265112962767D16D009B7607 /* day13.swift */; };
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 		269BE5BC2762959C00871C85 /* day8part2.swift in Sources */ = {isa = PBXBuildFile; fileRef = 269BE5BB2762959B00871C85 /* day8part2.swift */; };
@@ -106,6 +108,15 @@
 			);
 			runOnlyForDeploymentPostprocessing = 1;
 		};
+		263D3E37276E109D00B0AC5B /* CopyFiles */ = {
+			isa = PBXCopyFilesBuildPhase;
+			buildActionMask = 2147483647;
+			dstPath = /usr/share/man/man1/;
+			dstSubfolderSpec = 0;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 1;
+		};
 		2651128D2767D15A009B7607 /* CopyFiles */ = {
 			isa = PBXCopyFilesBuildPhase;
 			buildActionMask = 2147483647;
@@ -161,6 +172,8 @@
 		263CCF76276606670061B353 /* day12.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = day12.swift; sourceTree = "<group>"; };
 		263D3E2B276DDA5400B0AC5B /* Day17 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = Day17; sourceTree = BUILT_PRODUCTS_DIR; };
 		263D3E32276DDA6600B0AC5B /* day17.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = day17.swift; sourceTree = "<group>"; };
+		263D3E39276E109D00B0AC5B /* Day18 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = Day18; sourceTree = BUILT_PRODUCTS_DIR; };
+		263D3E41276E10AE00B0AC5B /* day18.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = day18.swift; sourceTree = "<group>"; };
 		2651128F2767D15A009B7607 /* Day13 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = Day13; sourceTree = BUILT_PRODUCTS_DIR; };
 		265112962767D16D009B7607 /* day13.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = day13.swift; sourceTree = "<group>"; };
 		269BE5B42762958800871C85 /* Day8Part2 */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = Day8Part2; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -229,6 +242,13 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
+		263D3E36276E109D00B0AC5B /* Frameworks */ = {
+			isa = PBXFrameworksBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
 		2651128C2767D15A009B7607 /* Frameworks */ = {
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
@@ -263,6 +283,7 @@
 		263BA594275E974800839C92 = {
 			isa = PBXGroup;
 			children = (
+				263D3E41276E10AE00B0AC5B /* day18.swift */,
 				263D3E32276DDA6600B0AC5B /* day17.swift */,
 				26EA5DFF276BA680003E0305 /* day16.swift */,
 				26155467276A6D0A00374D18 /* day15.swift */,
@@ -295,6 +316,7 @@
 				26155460276A6CF700374D18 /* Day15 */,
 				26EA5DF7276BA668003E0305 /* Day16 */,
 				263D3E2B276DDA5400B0AC5B /* Day17 */,
+				263D3E39276E109D00B0AC5B /* Day18 */,
 			);
 			name = Products;
 			sourceTree = "<group>";
@@ -438,6 +460,23 @@
 			productReference = 263D3E2B276DDA5400B0AC5B /* Day17 */;
 			productType = "com.apple.product-type.tool";
 		};
+		263D3E38276E109D00B0AC5B /* Day18 */ = {
+			isa = PBXNativeTarget;
+			buildConfigurationList = 263D3E3D276E109D00B0AC5B /* Build configuration list for PBXNativeTarget "Day18" */;
+			buildPhases = (
+				263D3E35276E109D00B0AC5B /* Sources */,
+				263D3E36276E109D00B0AC5B /* Frameworks */,
+				263D3E37276E109D00B0AC5B /* CopyFiles */,
+			);
+			buildRules = (
+			);
+			dependencies = (
+			);
+			name = Day18;
+			productName = Day18;
+			productReference = 263D3E39276E109D00B0AC5B /* Day18 */;
+			productType = "com.apple.product-type.tool";
+		};
 		2651128E2767D15A009B7607 /* Day13 */ = {
 			isa = PBXNativeTarget;
 			buildConfigurationList = 265112952767D15A009B7607 /* Build configuration list for PBXNativeTarget "Day13" */;
@@ -547,6 +586,9 @@
 						CreatedOnToolsVersion = 13.2;
 						LastSwiftMigration = 1320;
 					};
+					263D3E38276E109D00B0AC5B = {
+						CreatedOnToolsVersion = 13.2;
+					};
 					2651128E2767D15A009B7607 = {
 						CreatedOnToolsVersion = 13.1;
 						LastSwiftMigration = 1310;
@@ -588,6 +630,7 @@
 				2615545F276A6CF700374D18 /* Day15 */,
 				26EA5DF6276BA668003E0305 /* Day16 */,
 				263D3E2A276DDA5400B0AC5B /* Day17 */,
+				263D3E38276E109D00B0AC5B /* Day18 */,
 			);
 		};
 /* End PBXProject section */
@@ -665,6 +708,15 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
+		263D3E35276E109D00B0AC5B /* Sources */ = {
+			isa = PBXSourcesBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+				263D3E40276E10A500B0AC5B /* common.swift in Sources */,
+				263D3E42276E10AE00B0AC5B /* day18.swift in Sources */,
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
 		2651128B2767D15A009B7607 /* Sources */ = {
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
@@ -1075,6 +1127,30 @@
 			};
 			name = Release;
 		};
+		263D3E3E276E109D00B0AC5B /* Debug */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Automatic;
+				DEVELOPMENT_TEAM = 722B335UM5;
+				ENABLE_HARDENED_RUNTIME = YES;
+				MACOSX_DEPLOYMENT_TARGET = 12.1;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Debug;
+		};
+		263D3E3F276E109D00B0AC5B /* Release */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Automatic;
+				DEVELOPMENT_TEAM = 722B335UM5;
+				ENABLE_HARDENED_RUNTIME = YES;
+				MACOSX_DEPLOYMENT_TARGET = 12.1;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Release;
+		};
 		265112932767D15A009B7607 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
@@ -1275,6 +1351,15 @@
 			defaultConfigurationIsVisible = 0;
 			defaultConfigurationName = Release;
 		};
+		263D3E3D276E109D00B0AC5B /* Build configuration list for PBXNativeTarget "Day18" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				263D3E3E276E109D00B0AC5B /* Debug */,
+				263D3E3F276E109D00B0AC5B /* Release */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
 		265112952767D15A009B7607 /* Build configuration list for PBXNativeTarget "Day13" */ = {
 			isa = XCConfigurationList;
 			buildConfigurations = (

day18.swift

@@ -0,0 +1,318 @@
+import Foundation
+
+@main
+struct Day18: Puzzle {
+    func run() {
+        let pairs = Scanner(string: input).all()
+        let first = pairs[0]
+        let result = pairs.dropFirst().reduce(first, +)
+        print(result.toString())
+        print("Part 1:", result.magnitude())
+
+        var largest = 0
+        for a in pairs {
+            for b in pairs where a !== b {
+                largest = max(largest, (a + b).magnitude())
+                largest = max(largest, (b + a).magnitude())
+            }
+        }
+        print("Part 2:", largest)
+    }
+}
+
+extension Scanner {
+    func pair() -> Pair? {
+        guard scanString("[") != nil else { return nil }
+        guard let leftPart = part() else { return nil }
+        guard scanString(",") != nil else { return nil }
+        guard let rightPart = part() else { return nil }
+        guard scanString("]") != nil else { return nil }
+        return Pair(leftPart, rightPart)
+    }
+
+    func part() -> Number? {
+        if let digits = scanInt() {
+            return Regular(value: digits)
+        }
+
+        return pair()
+    }
+
+    func all() -> [Pair] {
+        var result: [Pair] = []
+        while let pair = self.pair() {
+            result.append(pair)
+        }
+        assert(isAtEnd)
+        return result
+    }
+}
+
+struct ExplodeContext {
+    var lastRegular: Regular? = nil
+    var addToNextNumber: Int? = nil
+    var didExplode = false
+}
+
+enum Action {
+    case goOn
+    case stop
+    case replace(Number)
+}
+
+protocol Number: AnyObject {
+    func toString() -> String
+
+    func visitExplode(depth: Int, context: inout ExplodeContext) -> Action
+    func visitSplit(didSplit: inout Bool) -> Action
+
+    func magnitude() -> Int
+
+    func copy() -> Number
+}
+
+extension Number where Self == Pair {
+    static func parse(_ string: String) -> Self {
+        Scanner(string: string).pair()!
+    }
+}
+
+class Regular: Number {
+    var value: Int
+
+    init(value: Int) {
+        self.value = value
+    }
+
+    func toString() -> String {
+        "\(value)"
+    }
+
+    func visitExplode(depth: Int, context: inout ExplodeContext) -> Action {
+        if let add = context.addToNextNumber {
+            value += add
+            return .stop
+        }
+
+        context.lastRegular = self
+        return .goOn
+    }
+
+    func visitSplit(didSplit: inout Bool) -> Action {
+        if value >= 10 {
+            let first = value / 2
+            didSplit = true
+            return .replace(Pair(Regular(value: first), Regular(value: value - first)))
+        }
+
+        return .goOn
+    }
+
+    func magnitude() -> Int {
+         value
+    }
+
+    func copy() -> Number { Regular(value: value) }
+
+}
+
+class Pair: Number {
+    var left: Number
+    var right: Number
+
+    init(_ left: Number, _ right: Number) {
+        self.left = left
+        self.right = right
+    }
+
+    func toString() -> String {
+        "[\(left.toString()), \(right.toString())]"
+    }
+
+    func splitFirst() -> Bool {
+        var didSplit = false
+        _ = visitSplit(didSplit: &didSplit)
+        return didSplit
+    }
+
+    func explodeFirst() -> Bool {
+        var context = ExplodeContext()
+        _ = visitExplode(depth: 0, context: &context)
+        return context.didExplode
+    }
+
+    func reduce() -> Pair {
+        while true {
+            if explodeFirst() { continue }
+            if splitFirst() { continue }
+            break
+        }
+
+        return self
+    }
+
+    func visitExplode(depth: Int, context: inout ExplodeContext) -> Action {
+        if !context.didExplode && depth == 4 {
+            context.lastRegular?.value += (left as! Regular).value
+            context.addToNextNumber = (right as! Regular).value
+            context.didExplode = true
+            return .replace(Regular(value: 0))
+        }
+
+
+        switch left.visitExplode(depth: depth + 1, context: &context) {
+        case .goOn:
+            break
+        case .stop:
+            return .stop
+        case .replace(let number):
+            left = number
+            break
+        }
+
+        let result = right.visitExplode(depth: depth + 1, context: &context)
+        switch result {
+        case .goOn:
+            return .goOn
+        case .stop:
+            return .stop
+        case .replace(let number):
+            right = number
+            return .goOn
+        }
+
+    }
+
+    func visitSplit(didSplit: inout Bool) -> Action {
+        switch left.visitSplit(didSplit: &didSplit) {
+        case .goOn: break
+        case .stop: return .stop
+        case .replace(let new):
+            left = new
+            return .stop
+        }
+
+        switch right.visitSplit(didSplit: &didSplit) {
+        case .goOn: return .goOn
+        case .stop: return .stop
+        case .replace(let new):
+            right = new
+            return .stop
+        }
+    }
+
+    func magnitude() -> Int {
+        3 * left.magnitude() + 2 * right.magnitude()
+    }
+
+    func copy() -> Number {
+        Pair(left.copy(), right.copy())
+    }
+}
+
+func +(lhs: Number, rhs: Number) -> Pair {
+    Pair(lhs.copy(), rhs.copy()).reduce()
+}
+
+let input = """
+[4,[3,[9,[9,0]]]]
+[[[7,6],[2,[2,5]]],[5,[[7,3],8]]]
+[4,[4,6]]
+[[0,[5,6]],[[[1,3],[2,7]],[[0,6],4]]]
+[6,[[3,[6,0]],3]]
+[[7,[9,[8,5]]],[6,7]]
+[[[[2,6],1],2],[3,[8,4]]]
+[4,[[[5,4],[2,7]],[[8,0],[2,3]]]]
+[[[[4,3],2],[[3,6],[2,5]]],[[[3,7],8],0]]
+[[[8,[0,7]],1],[[9,[3,9]],9]]
+[[[[3,0],[1,3]],[[0,9],8]],[[[7,2],9],[[1,4],[3,5]]]]
+[[[[9,6],[4,4]],[1,3]],[[4,3],[[6,4],[8,4]]]]
+[[[1,2],[[7,6],[2,3]]],[[4,6],[4,2]]]
+[[[4,8],[[5,8],1]],[2,3]]
+[[[5,2],[3,[5,7]]],[[2,9],5]]
+[[[6,[3,2]],[2,6]],[[8,[4,2]],[[5,2],7]]]
+[[[[2,6],[0,1]],[7,[3,6]]],[[1,6],[[7,9],0]]]
+[[[0,3],[8,1]],[[[9,0],3],[0,2]]]
+[[8,[[7,1],[4,7]]],[[0,[1,3]],[8,2]]]
+[[[[2,3],4],[[0,8],[9,0]]],[1,[[5,3],4]]]
+[[[[7,2],2],[[1,3],[8,3]]],[4,[[7,9],[0,6]]]]
+[[[[2,2],[3,4]],[[1,5],[4,3]]],[6,[[7,2],1]]]
+[1,[[[5,7],0],[9,[8,8]]]]
+[[[[9,2],[0,9]],[4,[7,8]]],[[4,8],[[1,8],[4,9]]]]
+[[[[4,7],2],2],4]
+[1,[[2,[4,2]],1]]
+[[[[7,2],[3,8]],[0,[1,3]]],[[[4,4],[2,4]],[8,2]]]
+[[[[1,0],[0,5]],2],[[9,[5,0]],[[1,6],5]]]
+[4,[[[8,1],[1,4]],[7,[1,3]]]]
+[[[6,[0,4]],[[4,6],[2,4]]],[9,[1,5]]]
+[[[[3,6],[3,3]],1],[0,[[8,8],2]]]
+[[7,[5,[2,6]]],[[[7,9],6],[0,[3,6]]]]
+[[[[6,7],4],[[2,9],2]],3]
+[[[7,[1,7]],[5,4]],[[[1,1],[0,1]],5]]
+[[6,[[1,0],6]],[0,[6,[0,5]]]]
+[[[[2,4],[4,6]],9],[4,[[8,0],7]]]
+[[[[9,9],[5,7]],[9,[8,6]]],[[3,[2,3]],0]]
+[[0,[1,[5,3]]],[3,[8,[3,4]]]]
+[[[[4,3],8],[2,9]],[[1,[6,5]],[[5,7],2]]]
+[[[0,[7,4]],[9,[9,6]]],[[8,[5,5]],[[6,4],1]]]
+[[[[7,3],[7,9]],[8,[6,2]]],[[8,[4,5]],[[6,4],[6,7]]]]
+[[7,[[9,0],[9,0]]],[[[0,8],2],[8,[8,3]]]]
+[4,[7,[5,6]]]
+[7,[[[3,8],8],3]]
+[[[4,[6,6]],0],[9,0]]
+[[[[7,4],8],8],[[0,1],[[0,0],[2,4]]]]
+[7,[1,[[9,4],[3,6]]]]
+[[[[2,8],9],[[8,6],[2,2]]],[[[5,1],9],[2,[0,7]]]]
+[8,7]
+[[[[0,8],4],[[9,9],[9,9]]],[[[4,3],[1,0]],[6,8]]]
+[[[[8,3],[8,9]],1],[[4,[1,0]],[[4,0],[2,3]]]]
+[[[[4,7],[1,3]],[6,9]],[[1,0],[[1,8],5]]]
+[[2,[4,[6,5]]],[3,[[9,9],5]]]
+[[[[7,6],4],9],[8,[4,5]]]
+[[[0,[6,6]],[7,[8,9]]],[[[0,0],[3,4]],[4,[1,8]]]]
+[[[9,[7,0]],[5,8]],[6,[[5,0],[0,6]]]]
+[[[[4,0],[1,9]],[7,[3,6]]],[[2,[8,6]],[[2,8],[8,2]]]]
+[[[9,6],8],[[[5,5],[4,8]],0]]
+[[[[1,7],1],2],[[[6,8],3],[[3,3],5]]]
+[3,[5,[[3,8],6]]]
+[3,[[[9,6],[5,8]],[9,2]]]
+[[6,1],[6,4]]
+[[2,6],[[[1,2],2],8]]
+[[[[1,7],[3,6]],[2,[0,2]]],[[3,0],9]]
+[1,[[0,[4,9]],5]]
+[[[[5,5],[5,2]],[0,[6,4]]],8]
+[0,[7,[[6,9],[6,0]]]]
+[[[[2,2],[4,7]],[[7,4],6]],[[0,[1,7]],[[3,2],6]]]
+[[9,8],0]
+[[[[5,4],[4,8]],2],[3,[8,9]]]
+[[[[7,0],8],5],[2,6]]
+[[[5,[0,8]],5],[[[5,0],[1,8]],[[0,2],7]]]
+[[[[9,4],8],[[6,5],4]],[[5,[8,9]],[4,[0,4]]]]
+[[[[3,6],7],[[9,3],7]],[7,[[8,3],9]]]
+[[[[0,7],5],[[5,7],2]],[[2,[9,5]],[[7,7],[5,0]]]]
+[[[[7,5],2],[8,6]],[[2,[6,2]],[5,[3,1]]]]
+[[9,[9,1]],6]
+[[[0,7],[[5,9],2]],3]
+[[[9,3],[8,8]],[0,[4,5]]]
+[[[[6,2],5],[4,[3,1]]],[9,[2,8]]]
+[[[1,[9,4]],[[0,0],2]],[[1,[2,1]],[[7,8],[3,2]]]]
+[[[[0,6],[8,9]],[[4,7],[5,6]]],[[[1,4],[8,7]],[4,6]]]
+[[[[6,4],[1,5]],[0,8]],[[[9,7],[1,2]],[9,4]]]
+[[[[4,5],[0,7]],[9,[1,8]]],[[[5,0],6],7]]
+[[[0,[6,9]],[5,[5,6]]],7]
+[[4,5],[[7,[6,5]],1]]
+[[[7,9],[6,7]],[4,1]]
+[[[[9,6],1],[[3,1],[9,7]]],[1,[7,1]]]
+[[[0,[2,0]],5],[[8,[7,6]],[[7,3],4]]]
+[[[6,[1,7]],[9,[2,7]]],3]
+[[[6,[8,2]],5],[4,[[1,3],[5,1]]]]
+[[[4,[3,3]],[4,[2,4]]],[5,4]]
+[[[1,6],[4,[4,0]]],[[8,[2,2]],[[8,1],[4,7]]]]
+[[2,0],[[2,1],[[4,8],[2,7]]]]
+[9,[[8,4],0]]
+[[1,6],[[5,[1,3]],[9,[0,9]]]]
+[[[0,[3,5]],3],[[2,[8,0]],[[2,0],[4,3]]]]
+[[[1,[1,9]],[9,[7,9]]],[[2,2],[[6,7],[0,7]]]]
+[[[4,6],[[6,2],[0,9]]],[[1,0],[1,[6,7]]]]
+[9,[[[0,1],4],[[9,3],3]]]
+"""