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ThibaultKleinThibaultKlein
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Implemented Queue data structure using array andstack techniques
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6 files changed

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6 files changed

+344
-2
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‎DevKit/DevKit.xcodeproj/project.pbxproj‎

Lines changed: 38 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -42,11 +42,16 @@
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127+
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@@ -485,11 +495,21 @@
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name = Pods;
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sourceTree = "<group>";
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};
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8E54C4332142E906003207CC /* Queue */ = {
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isa = PBXGroup;
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children = (
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8E54C4342142E91A003207CC /* QueueArrayTests.swift */,
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8E54C4362142EA73003207CC /* QueueStackTests.swift */,
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);
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path = Queue;
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sourceTree = "<group>";
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};
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8E8F4AB22138696E00E2FD66 /* Data Structures */ = {
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isa = PBXGroup;
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children = (
491-
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8E8F4AB32138697600E2FD66 /* Linked List */,
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8E8F4AC32141B17300E2FD66 /* Queue */,
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8E8F4ABD2139C6D800E2FD66 /* Stack */,
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8E54C4332142E906003207CC /* Queue */,
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8E8F4AC02139C86700E2FD66 /* Stack */,
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@@ -544,6 +565,16 @@
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path = Stack;
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sourceTree = "<group>";
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};
568+
8E8F4AC32141B17300E2FD66 /* Queue */ = {
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isa = PBXGroup;
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children = (
571+
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path = Queue;
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sourceTree = "<group>";
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};
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8ED0CABB2141D14500F05CD6 /* QueueStack.swift in Sources */,
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205246D5209BA3200067A328 /* TransitioningNavigationViewOptions.swift in Sources */,
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8E8F4AC52141B18A00E2FD66 /* QueueArray.swift in Sources */,
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8E8F4AB52138698B00E2FD66 /* LinkedListNode.swift in Sources */,
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205246D3209B9E8F0067A328 /* TransitioningNavigationView.swift in Sources */,
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8E8F4AC22139C87300E2FD66 /* StackTests.swift in Sources */,
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8E54C4352142E91A003207CC /* QueueArrayTests.swift in Sources */,
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8E54C4372142EA73003207CC /* QueueStackTests.swift in Sources */,
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8E8F4ABC2138731500E2FD66 /* LinkedListTests.swift in Sources */,
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runOnlyForDeploymentPostprocessing = 0;

‎DevKit/DevKit/Classes/Data Structures/Queue/QueueArray.swift‎

Lines changed: 70 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,70 @@
1+
//
2+
// QueueArray.swift
3+
// DevKit
4+
//
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// Created by Thibault Klein on 9/6/18.
6+
// Copyright © 2018 Jonathan Samudio. All rights reserved.
7+
//
8+
9+
import Foundation
10+
11+
/// QueueArray.
12+
/// A queue is a collection of elements following a First-In-First-Out (FIFO) order.
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/// This implementation uses an array to store the elements.
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///
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/// - Note:
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/// Use a Queue if you need a sequence ordered as FIFO.
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///
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/// - The advantage of using an array is its simplicity and relative low memory impact.
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/// - The disadvantage is a O(n) complexity every time an element gets dequeued.
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/// Very large queues will have a bad performance using QueueArray.
21+
open class QueueArray<T>: Queueable {
22+
public typealias Element = T
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// MARK: - Public Properties
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/// `true` if the stack is empty. `false` if not.
27+
public var isEmpty: Bool {
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return peek() == nil
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}
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// MARK: - Private Properties
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private var storage: [Element] = []
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// MARK: - Initialization
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public init() { }
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// MARK: - Public Functions
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// MARK: General Functions
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/// Returns the value at the end of the queue.
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///
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/// - Complexity: O(1)
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/// - Returns: The value at the end of the queue.
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public func peek() -> Element? {
47+
return storage.last
48+
}
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// MARK: Adding Functions
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/// Enqueues an element at the beginning of the queue.
53+
///
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/// - Complexity: O(1)
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/// - Parameter value: The value to enqueue.
56+
public func enqueue(_ value: Element) {
57+
storage.append(value)
58+
}
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// MARK: Removing Functions
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/// Dequeues the element at the end of the queue.
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///
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/// - Complexity: O(n)
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/// - Returns: The dequeued element.
66+
public func dequeue() -> Element? {
67+
return isEmpty ? nil : storage.removeFirst()
68+
}
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}

‎DevKit/DevKit/Classes/Data Structures/Queue/QueueStack.swift‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,75 @@
1+
//
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// QueueStack.swift
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// DevKit
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//
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// Created by Thibault Klein on 9/6/18.
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// Copyright © 2018 Jonathan Samudio. All rights reserved.
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//
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9+
import Foundation
10+
11+
/// QueueStack.
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/// A queue is a collection of elements following a First-In-First-Out (FIFO) order.
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/// This implementation uses two stacks to store the elements.
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///
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/// - Note:
16+
/// Use a Queue if you need a sequence ordered as FIFO.
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///
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/// - The advantage of using two stack is constant complexity when enqueueing and dequeueing.
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/// QueueStack has better performance when working with large queues than QueueArray.
20+
open class QueueStack<T>: Queueable {
21+
public typealias Element = T
22+
23+
// MARK: - Public Properties
24+
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/// `true` if the stack is empty. `false` if not.
26+
public var isEmpty: Bool {
27+
return leftStack.isEmpty && rightStack.isEmpty
28+
}
29+
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// MARK: - Private Properties
31+
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private var leftStack: [T] = []
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private var rightStack: [T] = []
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// MARK: - Initialization
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public init() { }
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// MARK: - Public Functions
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// MARK: General Functions
41+
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/// Returns the value at the end of the queue.
43+
///
44+
/// - Complexity: O(1)
45+
/// - Returns: The value at the end of the queue.
46+
public func peek() -> T? {
47+
return !leftStack.isEmpty ? leftStack.last : rightStack.first
48+
}
49+
50+
// MARK: Adding Functions
51+
52+
/// Enqueues an element at the beginning of the queue.
53+
///
54+
/// - Complexity: O(1)
55+
/// - Parameter value: The value to enqueue.
56+
public func enqueue(_ value: T) {
57+
rightStack.append(value)
58+
}
59+
60+
// MARK: Removing Functions
61+
62+
/// Dequeues the element at the end of the queue.
63+
///
64+
/// - Complexity: O(1)
65+
/// - Returns: The dequeued element.
66+
public func dequeue() -> T? {
67+
if leftStack.isEmpty {
68+
leftStack = rightStack.reversed()
69+
rightStack.removeAll()
70+
}
71+
72+
return leftStack.popLast()
73+
}
74+
75+
}

‎DevKit/DevKit/Classes/Data Structures/Queue/Queueable.swift‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
1+
//
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// Queueable.swift
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// DevKit
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//
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// Created by Thibault Klein on 9/6/18.
6+
// Copyright © 2018 Jonathan Samudio. All rights reserved.
7+
//
8+
9+
import Foundation
10+
11+
/// Defines how a queue can be implemented.
12+
/// There are different techniques you can use to create a queue (array, doubly linked list, ring buffer, double stack...)
13+
/// that can confirm to this protocol.
14+
public protocol Queueable {
15+
associatedtype Element
16+
17+
var isEmpty: Bool { get }
18+
19+
func peek() -> Element?
20+
func enqueue(_ value: Element)
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func dequeue() -> Element?
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23+
}

‎DevKit/DevKitTests/Classes/Data Structures/Queue/QueueArrayTests.swift‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,69 @@
1+
//
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// QueueArrayTests.swift
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// DevKitTests
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//
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// Created by Thibault Klein on 9/7/18.
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// Copyright © 2018 Jonathan Samudio. All rights reserved.
7+
//
8+
9+
import DevKit
10+
import XCTest
11+
12+
class QueueArrayTests: XCTestCase {
13+
14+
func test_queueArray_IsEmpty_EmptyList() {
15+
// Given
16+
let queue = QueueArray<Int>()
17+
// Then
18+
XCTAssertTrue(queue.isEmpty)
19+
}
20+
21+
func test_queueArray_IsEmpty_NonEmptyList() {
22+
// Given
23+
let queue = QueueArray<Int>()
24+
// When
25+
queue.enqueue(1)
26+
// Then
27+
XCTAssertFalse(queue.isEmpty)
28+
}
29+
30+
func test_queueArray_Peek_EmptyList() {
31+
// Given
32+
let queue = QueueArray<Int>()
33+
// Then
34+
XCTAssertNil(queue.peek())
35+
}
36+
37+
func test_queueArray_Enqueue() {
38+
// Given
39+
let queue = QueueArray<Int>()
40+
XCTAssertNil(queue.peek())
41+
// When
42+
queue.enqueue(1)
43+
// Then
44+
XCTAssertEqual(queue.peek()!, 1)
45+
}
46+
47+
func test_queueArray_Dequeue_EmptyList() {
48+
// Given
49+
let queue = QueueArray<Int>()
50+
XCTAssertNil(queue.peek())
51+
// When
52+
queue.enqueue(1)
53+
// Then
54+
XCTAssertEqual(queue.dequeue()!, 1)
55+
}
56+
57+
func test_queueArray_Dequeue() {
58+
// Given
59+
let queue = QueueArray<Int>()
60+
XCTAssertNil(queue.peek())
61+
// When
62+
queue.enqueue(1)
63+
queue.enqueue(2)
64+
queue.enqueue(3)
65+
// Then
66+
XCTAssertEqual(queue.dequeue()!, 1)
67+
}
68+
69+
}

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