d24p1

day24/d24p1.swift

@@ -0,0 +1,73 @@
+import Foundation
+
+typealias Op = (Bool, Bool) -> Bool
+typealias Gate  = (String, Op, String, String)
+
+struct Circuit : CustomStringConvertible {
+    let gates: [Gate]
+    var nodes: [String: Bool]
+    var pendingEndNodes: Set<String>
+    var description: String {
+        nodes.map { "\($0): \($1 ? 1 : 0)" }.sorted().joined(separator: "\n") +
+        "\n\(pendingEndNodes)"
+    }
+    var value: Int? {
+        if pendingEndNodes.count > 0 { return nil }
+        return nodes.keys.filter { $0.starts(with: "z") }
+            .sorted().reversed().reduce(0) { $0*2 + (nodes[$1]! ? 1 : 0) }
+    }
+    mutating func run(gate: Gate) {
+        let (in1, op, in2, out) = gate
+        if let v1 = nodes[in1], let v2 = nodes[in2] {
+            nodes[out] = op(v1, v2)
+            pendingEndNodes.remove(out)
+        }
+    }
+    mutating func run() {
+        gates.forEach { run(gate: $0) }
+    }
+}
+
+func readInput(_ filePath: String) throws -> Circuit {
+    let content = try String(contentsOfFile: filePath, encoding: .ascii)
+    let nodeRe = try Regex(#"([a-z0-9]+): (0|1)"#)
+    let gateRe = try Regex(#"([a-z0-9]+) (AND|OR|XOR) ([a-z0-9]+) -> ([a-z0-9]+)"#)
+    let opMap: [String: Op] = [
+        "AND": { $0 && $1 },
+        "OR": { $0 || $1 },
+        "XOR": { $0 != $1 }
+    ]
+    var nodes: [String: Bool] = [:]
+    var gates: [Gate] = []
+    var endNodes: Set<String> = []
+    for line in content.split(separator: "\n") {
+        if let m = line.wholeMatch(of: nodeRe) {
+            let node = String(m.output[1].substring!)
+            let val = m.output[2].substring! == "1"
+            nodes[node] = val
+        }
+        if let m = line.wholeMatch(of: gateRe) {
+            let in1 = String(m.output[1].substring!)
+            let op = opMap[String(m.output[2].substring!)]!
+            let in2 = String(m.output[3].substring!)
+            let out = String(m.output[4].substring!)
+            gates.append((in1, op, in2, out))
+            if out.starts(with: "z") {
+                endNodes.insert(out)
+            }
+        }
+    }
+    return Circuit(gates: gates, nodes: nodes, pendingEndNodes: endNodes)
+} 
+
+var circuit = try readInput(CommandLine.arguments[1])
+//print(circuit)
+while true {
+    if let res = circuit.value {
+        print("answer: \(res)")
+        break
+    }
+    circuit.run()
+    //print(circuit)
+}
+