Add 2015

2015/Day14.playground/Contents.swift

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+import Foundation
+
+let regex = try! NSRegularExpression(pattern: #"^([a-z]+) can fly (\d+) km/s for (\d+) seconds, but then must rest for (\d+) seconds.$"#, options: [.caseInsensitive, .anchorsMatchLines])
+
+struct Reindeer {
+    var name: String
+    var flySpeed: Int
+    var flyDuration: Int
+    var restDuration: Int
+
+    var duration: Int
+    var resting: Bool = false
+    var distance: Int = 0
+    var points: Int = 0
+
+    mutating func step() {
+        duration -= 1
+        if !resting {
+            distance += flySpeed
+        }
+
+        if duration == 0 {
+            resting.toggle()
+            duration = resting ? restDuration : flyDuration
+        }
+    }
+
+    static func parse(_ input: String) -> [Reindeer] {
+        let matches = regex.matches(in: input, options: [], range: NSRange(input.startIndex..., in: input))
+        return matches.map { Reindeer(match: $0, in: input) }
+    }
+
+    init(match: NSTextCheckingResult, in string: String) {
+        name = String(match.string(index: 1, in: string))
+        flySpeed = Int(match.string(index: 2, in: string))!
+        flyDuration = Int(match.string(index: 3, in: string))!
+        restDuration = Int(match.string(index: 4, in: string))!
+
+        duration = flyDuration
+    }
+}
+
+extension NSTextCheckingResult {
+    func string(index: Int, in string: String) -> Substring {
+        let range = Range(self.range(at: index), in: string)!
+        return string[range]
+    }
+}
+
+let input = """
+Vixen can fly 19 km/s for 7 seconds, but then must rest for 124 seconds.
+Rudolph can fly 3 km/s for 15 seconds, but then must rest for 28 seconds.
+Donner can fly 19 km/s for 9 seconds, but then must rest for 164 seconds.
+Blitzen can fly 19 km/s for 9 seconds, but then must rest for 158 seconds.
+Comet can fly 13 km/s for 7 seconds, but then must rest for 82 seconds.
+Cupid can fly 25 km/s for 6 seconds, but then must rest for 145 seconds.
+Dasher can fly 14 km/s for 3 seconds, but then must rest for 38 seconds.
+Dancer can fly 3 km/s for 16 seconds, but then must rest for 37 seconds.
+Prancer can fly 25 km/s for 6 seconds, but then must rest for 143 seconds.
+"""
+
+
+var group = Reindeer.parse(input)
+
+for _ in 0..<2503 {
+    for i in group.indices {
+        group[i].step()
+    }
+
+    let lead = group.map(\.distance).max()!
+
+    for i in group.indices where group[i].distance == lead {
+        group[i].points += 1
+    }
+}
+
+group
+
+group
+    .sorted { $0.points > $1.points }
+    .first
+