2022 Day 11 part 1

2022/day11.swift

@@ -0,0 +1,136 @@
+import Foundation
+
+typealias Item = Int
+
+class Monkey {
+    var items: [Item]
+    var operation: Operation
+    var operand: Operand
+    var test: Int
+    var trueTarget: Int
+    var falseTarget: Int
+    var inspectCount = 0
+    
+    init(items: [Item], operation: Operation, operand: Operand, test: Int, trueTarget: Int, falseTarget: Int) {
+        self.items = items
+        self.operation = operation
+        self.operand = operand
+        self.test = test
+        self.trueTarget = trueTarget
+        self.falseTarget = falseTarget
+    }
+    
+    func run() {
+        for item in items {
+            inspectCount += 1
+            let newLevel = operation.apply(item, operand.value(item: item)) / 3
+            let target = newLevel.isMultiple(of: test) ? trueTarget : falseTarget
+            monkeys[target].add(newLevel)
+        }
+        items.removeAll()
+    }
+    
+    func add(_ item: Item) {
+        items.append(item)
+    }
+}
+
+extension Monkey {
+    convenience init?(scanner: Scanner) {
+        guard scanner.scanString("Monkey") != nil, scanner.scanInt() != nil, scanner.scanString(":") != nil else {
+            return nil
+        }
+        
+        guard scanner.scanString("Starting items:") != nil else { return nil }
+        let items = scanner.scanList().map(Item.init(_:))
+        
+        guard scanner.scanString("Operation: new = old") != nil, let operation = scanner.scanOperation(), let operand = scanner.scanOperand() else { return nil }
+        
+        guard scanner.scanString("Test: divisible by") != nil, let test = scanner.scanInt() else { return nil }
+        guard scanner.scanString("If true: throw to monkey") != nil, let trueTarget = scanner.scanInt() else { return nil }
+        guard scanner.scanString("If false: throw to monkey") != nil, let falseTarget = scanner.scanInt() else { return nil }
+        
+        self.init(items: items, operation: operation, operand: operand, test: test, trueTarget: trueTarget, falseTarget: falseTarget)
+    }
+}
+
+
+enum Operation: String, CaseIterable {
+    case add = "+"
+    case multiply = "*"
+    
+    func apply(_ lhs: Item, _ rhs: Item) -> Item {
+        switch self {
+            case .add: return lhs + rhs
+            case .multiply: return lhs * rhs
+        }
+    }
+}
+
+enum Operand {
+    case number(Int)
+    case old
+    
+    func value(item: Item) -> Item {
+        switch self {
+            case .number(let number): return Item(number)
+            case .old: return item
+        }
+    }
+}
+
+extension Scanner {
+    func scanList() -> [Int] {
+        var result: [Int] = []
+        while true {
+            guard let int = scanInt() else {
+                break
+            }
+            result.append(int)
+            guard scanString(",") != nil else {
+                break
+            }
+        }
+        return result
+    }
+    
+    func scanOperation() -> Operation? {
+        for op in Operation.allCases {
+            if scanString(op.rawValue) != nil {
+                return op
+            }
+        }
+        return nil
+    }
+    
+    func scanOperand() -> Operand? {
+        if let int = scanInt() {
+            return .number(int)
+        }
+        
+        if scanString("old") != nil {
+            return .old
+        }
+        
+        return nil
+    }
+}
+
+let input = try String(contentsOf: URL(fileURLWithPath: "day11.input"))
+let scanner = Scanner(string: input)
+var monkeys: [Monkey] = []
+
+while !scanner.isAtEnd, let monkey = Monkey(scanner: scanner) {
+    monkeys.append(monkey)
+}
+
+
+for _ in 0..<20 {
+    for monkey in monkeys {
+        monkey.run()
+    }
+}
+
+
+let monkeyBusiness = monkeys.map(\.inspectCount).sorted(by: >).prefix(2).reduce(1, *)
+print("Part 1:", monkeyBusiness)