Create 3.6 Animal Shelter.swift

Ch 3. Stacks and Queues/Ch 3. Stacks and Queues.playground/Pages/3.6 Animal Shelter.swift

@@ -0,0 +1,49 @@
+enum AnimalType: Int {
+    case cat = 0
+    case dog = 1
+}
+
+
+public class Animal {
+
+    let animalType: AnimalType
+
+    init(animalType: AnimalType) {
+        self.animalType = animalType
+    }
+}
+
+extension Animal: Equatable {
+    public static func == (lhs: Animal, rhs: Animal) -> Bool {
+        return lhs.animalType == rhs.animalType
+    }
+}
+
+public class AnimalQueue {
+    private var items: [Animal] = []
+
+    func enqueue(_ item: Animal) {
+        items.append(item)
+    }
+
+    func dequeue() -> Animal? {
+        guard items.count > 0 else { return nil }
+        return items.removeFirst()
+    }
+
+    func dequeue(animalType: AnimalType) -> Animal? {
+        guard items.count > 0 else { return nil }
+        for index in 0..<items.count {
+            if items[index].animalType == animalType {
+                let firstOfType = items[index]
+                items.remove(at: index)
+                return firstOfType
+            }
+        }
+        return nil
+    }
+
+    func isEmpty() -> Bool {
+        return items.isEmpty
+    }
+}