d19

day19/d19p2.swift

@@ -0,0 +1,37 @@
+import Foundation
+
+enum Color: Character, CustomStringConvertible {
+    case r = "r"
+    case g = "g"
+    case u = "u"
+    case w = "w"
+    case b = "b"
+    var description: String { return String(self.rawValue) }
+}
+
+func readInput(_ filePath: String) throws -> ([[Color]], [[Color]]) {
+    let content = try String(contentsOfFile: filePath, encoding: .ascii)
+    let lines = content.split(separator: "\n")
+    let towels = lines[0].split(separator: ", ").map { $0.compactMap(Color.init) }
+    let patterns = lines[1..<lines.count].map { $0.compactMap(Color.init) }
+    return (towels, patterns)
+}
+
+var cache: [[Color]: Int] = [:]
+func matches(_ pattern: [Color], _ towels: [[Color]]) -> Int {
+    if pattern.count == 0 {
+        return 1
+    }
+    if let cached = cache[pattern] {
+        return cached
+    }
+    let r = towels
+        .filter { pattern.starts(with: $0) }
+        .map { matches(Array(pattern[$0.count..<pattern.count]), towels) }
+        .reduce(0, +)
+    cache[pattern] = r
+    return r
+}
+
+let (towels, patterns) = try readInput(CommandLine.arguments[1])
+print(patterns.reduce(0) { s, p in s + matches(p, towels) })