Add a basic Queue data structure

Implemented as a linked list.

Terrain.xcodeproj/project.pbxproj

@@ -9,6 +9,8 @@
 /* Begin PBXBuildFile section */
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 		C018AD3B219518480094BE3C /* AlgorithmsTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = C018AD3A219518480094BE3C /* AlgorithmsTests.swift */; };
+		C018AD4021978E690094BE3C /* Queue.swift in Sources */ = {isa = PBXBuildFile; fileRef = C018AD3F21978E690094BE3C /* Queue.swift */; };
+		C018AD422197907B0094BE3C /* QueueTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = C018AD412197907B0094BE3C /* QueueTests.swift */; };
 		C019C8512191CE7100EAD5BB /* Uniforms.m in Sources */ = {isa = PBXBuildFile; fileRef = C019C8502191CE7100EAD5BB /* Uniforms.m */; };
 		C08C58A0218F46F000EAFC2D /* Algorithms.swift in Sources */ = {isa = PBXBuildFile; fileRef = C08C589F218F46F000EAFC2D /* Algorithms.swift */; };
 		C08C58A2218F474E00EAFC2D /* TerrainAlgorithms.metal in Sources */ = {isa = PBXBuildFile; fileRef = C08C58A1218F474E00EAFC2D /* TerrainAlgorithms.metal */; };
@@ -46,6 +48,8 @@
 		C018AD32219518080094BE3C /* Terrain2Tests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Terrain2Tests.swift; sourceTree = "<group>"; };
 		C018AD34219518080094BE3C /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		C018AD3A219518480094BE3C /* AlgorithmsTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AlgorithmsTests.swift; sourceTree = "<group>"; };
+		C018AD3F21978E690094BE3C /* Queue.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Queue.swift; sourceTree = "<group>"; };
+		C018AD412197907B0094BE3C /* QueueTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = QueueTests.swift; sourceTree = "<group>"; };
 		C019C8502191CE7100EAD5BB /* Uniforms.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = Uniforms.m; sourceTree = "<group>"; };
 		C08C589F218F46F000EAFC2D /* Algorithms.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Algorithms.swift; sourceTree = "<group>"; };
 		C08C58A1218F474E00EAFC2D /* TerrainAlgorithms.metal */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.metal; path = TerrainAlgorithms.metal; sourceTree = "<group>"; };
@@ -107,6 +111,7 @@
 			children = (
 				C018AD32219518080094BE3C /* Terrain2Tests.swift */,
 				C018AD3A219518480094BE3C /* AlgorithmsTests.swift */,
+				C018AD412197907B0094BE3C /* QueueTests.swift */,
 				C018AD34219518080094BE3C /* Info.plist */,
 			);
 			path = Terrain2Tests;
@@ -176,6 +181,7 @@
 				C0C15AB6218E2A90007494E2 /* Renderer.swift */,
 				C0C15AC5218E32B2007494E2 /* Terrain.swift */,
 				C08C589F218F46F000EAFC2D /* Algorithms.swift */,
+				C018AD3F21978E690094BE3C /* Queue.swift */,
 				C018AD3E219728890094BE3C /* Shaders */,
 				C0C15ABA218E2A90007494E2 /* ShaderTypes.h */,
 				C019C8502191CE7100EAD5BB /* Uniforms.m */,
@@ -318,6 +324,7 @@
 			buildActionMask = 2147483647;
 			files = (
 				C018AD33219518080094BE3C /* Terrain2Tests.swift in Sources */,
+				C018AD422197907B0094BE3C /* QueueTests.swift in Sources */,
 				C018AD3B219518480094BE3C /* AlgorithmsTests.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
@@ -346,6 +353,7 @@
 				C0C15AB7218E2A90007494E2 /* Renderer.swift in Sources */,
 				C0C15AB3218E2A90007494E2 /* AppDelegate.swift in Sources */,
 				C019C8512191CE7100EAD5BB /* Uniforms.m in Sources */,
+				C018AD4021978E690094BE3C /* Queue.swift in Sources */,
 				C08C58A0218F46F000EAFC2D /* Algorithms.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;

Terrain2/Algorithms.swift

@@ -222,11 +222,11 @@ public class DiamondSquareGenerator: TerrainGenerator {
         }
 
         func breadthFirstSearch(visit: (Box) -> (Void)) {
-            var queue = [self]
+            var queue = Queue<Box>()
-            while queue.count > 0 {
+            queue.enqueue(item: self)
-                let box = queue.removeFirst()
+            while let box = queue.dequeue() {
                 visit(box)
-                queue.append(contentsOf: box.subdivisions)
+                queue.enqueue(items: box.subdivisions)
             }
         }
     }

Terrain2/Queue.swift

@@ -0,0 +1,54 @@
+//
+//  Queue.swift
+//  Terrain2
+//
+//  Created by Eryn Wells on 11/10/18.
+//  Copyright © 2018 Eryn Wells. All rights reserved.
+//
+
+import Foundation
+
+struct Queue<Element> {
+    class Node<Element> {
+        var item: Element
+        var next: Node?
+
+        init(item i: Element) {
+            item = i
+        }
+    }
+
+    var count: Int = 0
+    var head: Node<Element>?
+    var tail: Node<Element>?
+
+    mutating func enqueue(item: Element) {
+        let newNode = Node(item: item)
+        if head == nil {
+            head = newNode
+            tail = newNode
+        } else {
+            tail!.next = newNode
+            tail = newNode
+        }
+        count += 1
+    }
+
+    mutating func enqueue<S>(items: S) where Element == S.Element, S : Sequence {
+        for i in items {
+            enqueue(item: i)
+        }
+    }
+
+    mutating func dequeue() -> Element? {
+        guard let oldHead = head else {
+            return nil
+        }
+        head = oldHead.next
+        if head == nil {
+            tail = nil
+        }
+        count -= 1
+        return oldHead.item
+    }
+}

Terrain2Tests/QueueTests.swift

@@ -0,0 +1,51 @@
+//
+//  QueueTests.swift
+//  Terrain2Tests
+//
+//  Created by Eryn Wells on 11/10/18.
+//  Copyright © 2018 Eryn Wells. All rights reserved.
+//
+
+import XCTest
+@testable import Terrain2
+
+class QueueTests: XCTestCase {
+
+    func testEnqueue() {
+        var queue = Queue<Int>()
+        queue.enqueue(item: 1)
+        queue.enqueue(item: 2)
+        queue.enqueue(item: 3)
+        XCTAssertEqual(queue.count, 3)
+        XCTAssertEqual(queue.head?.item, 1)
+        XCTAssertEqual(queue.head?.next?.item, 2)
+        XCTAssertEqual(queue.head?.next?.next?.item, 3)
+    }
+
+    func testDequeue() {
+        var queue = Queue<Int>()
+        queue.enqueue(item: 1)
+        queue.enqueue(item: 2)
+        queue.enqueue(item: 3)
+
+        XCTAssertEqual(queue.count, 3)
+        XCTAssertEqual(queue.head?.item, 1)
+        XCTAssertEqual(queue.tail?.item, 3)
+
+        XCTAssertEqual(queue.dequeue(), 1)
+        XCTAssertEqual(queue.count, 2)
+        XCTAssertEqual(queue.head?.item, 2)
+        XCTAssertEqual(queue.tail?.item, 3)
+
+        XCTAssertEqual(queue.dequeue(), 2)
+        XCTAssertEqual(queue.count, 1)
+        XCTAssertEqual(queue.head?.item, 3)
+        XCTAssertEqual(queue.tail?.item, 3)
+
+        XCTAssertEqual(queue.dequeue(), 3)
+        XCTAssertEqual(queue.count, 0)
+        XCTAssertNil(queue.head)
+        XCTAssertNil(queue.tail)
+    }
+
+}