d24p2

day24/d24p2.swift

@@ -30,22 +30,15 @@ struct Circuit : CustomStringConvertible {
 
 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!)]!
@@ -57,16 +50,29 @@ func readInput(_ filePath: String) throws -> Circuit {
             }
         }
     }
-    return Circuit(gates: gates, nodes: nodes, pendingEndNodes: endNodes)
+    return Circuit(gates: gates, nodes: [:], pendingEndNodes: endNodes)
 } 
 
+extension Int {
+    func toNodes(_ prefix: String) -> [String: Bool] {
+        var nodes: [String: Bool] = [:]
+        for i in (0..<45) {
+            nodes[prefix + String(format: "%02d", i)] = ((self >> i) & 1) == 1
+        }
+        return nodes
+    }
+}
+
 var circuit = try readInput(CommandLine.arguments[1])
+// generate random x y to try
+let x = Int.random(in: 0..<(1<<45))
+let y = Int.random(in: 0..<(1<<45))
+circuit.nodes.merge(x.toNodes("x")) { l, r in l }
+circuit.nodes.merge(y.toNodes("y")) { l, r in l }
 // just print out the wrong bits for manual debugging. See input.dot
+// print(circuit)
 while true {
-    if let z = circuit.value(of: "z"),
-        let x = circuit.value(of: "x"),
-        let y = circuit.value(of: "y")
-    {
+    if let z = circuit.value(of: "z") {
         print("x: " + String(x, radix: 2).reversed())
         print("y: " + String(y, radix: 2).reversed())
         let zStr = String(z, radix: 2).reversed()
@@ -82,3 +88,7 @@ while true {
     circuit.run()
 }
 
+// use graphviz to render input.dot to svg
+// run program to find out first bit that failed (highlighted in red)
+// look at svg around that for irregularities (regular full adders are obvious)
+// in this case z16 <-> fkb and z31 <-> rdn