Rock-paper-scissors: Difference between revisions

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 }
+</pre>
+=={{header|Swift}}==
+<lang Swift>enum Choice: CaseIterable {
+  case rock
+  case paper
+  case scissors
+  case lizard
+  case spock
+}
+extension Choice {
+  var weaknesses: Set<Choice> {
+    switch self {
+      case .rock:
+        return [.paper, .spock]
+      case .paper:
+        return [.scissors, .lizard]
+      case .scissors:
+        return [.rock, .spock]
+      case .lizard:
+        return [.rock, .scissors]
+      case .spock:
+        return [.paper, .lizard]
+    }
+  }
+}
+struct Game {
+  private(set) var history: [(Choice, Choice)] = []
+  private(set) var p1Score: Int = 0
+  private(set) var p2Score: Int = 0
+  mutating func play(_ p1Choice: Choice, against p2Choice: Choice) {
+    history.append((p1Choice, p2Choice))
+    if p2Choice.weaknesses.contains(p1Choice) {
+      p1Score += 1
+    } else if p1Choice.weaknesses.contains(p2Choice) {
+      p2Score += 1
+    }
+  }
+}
+func aiChoice(for game: Game) -> Choice {
+  if let weightedWeekness = game.history.flatMap({ $0.0.weaknesses }).randomElement() {
+    return weightedWeekness
+  } else {
+    // If history is empty, return random Choice
+    return Choice.allCases.randomElement()!
+  }
+}
+var game = Game()
+print("Type your choice to play a round, or 'q' to quit")
+loop: while true {
+  let choice: Choice
+  switch readLine().map({ $0.lowercased() }) {
+    case "r", "rock":
+      choice = .rock
+    case "p", "paper":
+      choice = .paper
+    case "scissors":
+      choice = .scissors
+    case "l", "lizard":
+      choice = .lizard
+    case "spock":
+      choice = .spock
+    case "q", "quit", "exit":
+      break loop
+    case "s":
+      print("Do you mean Spock, or scissors?")
+      continue
+    default:
+      print("Unknown choice. Type 'q' to quit")
+      continue
+  }
+  let p2Choice = aiChoice(for: game)
+  print("You played \(choice) against \(p2Choice)")
+  game.play(choice, against: p2Choice)
+  print("Current score: \(game.p1Score) : \(game.p2Score)")
+}</lang>
+'''Sample run:'''
+<pre>
+Type your choice to play a round, or 'q' to quit
+r
+You played rock against paper
+Current score: 0 : 1
+Paper
+You played paper against paper
+Current score: 0 : 1
+spock
+You played spock against lizard
+Current score: 0 : 2
+lizard
+You played lizard against paper
+Current score: 1 : 2
+q
 </pre>