add Queue Program using in Swift

Contributors.md

@@ -14,10 +14,8 @@
 * ![Nicolai Bonde](https://github.com/neobonde)
 * ![Tanmay Bhagwat](https://github.com/frizzid07)
 * ![Altaha Ansari](https://github.com/altaha-ansari)
-* ![Vedant Raghuwanshi](https://github.com/007vedant
-* ![Ana Ferreira](https://github.com/anacdf))
+* ![Vedant Raghuwanshi](https://github.com/007vedant)
+* ![Ana Ferreira](https://github.com/anacdf)
 * ![Prathima B](https://github.com/prathima-b)
+* ![Stevhen](https://github.com/stevhens)
 * ![Shristi Raj](https://github.com/enazuma11)
-
-
-

Simple_Queue/queue.swift

@@ -0,0 +1,271 @@
+//
+//  queue.swift
+//  Queue
+//
+//  Created by Steven Sim on 8/10/19.
+//  Copyright © 2019 Steven Sim. All rights reserved.
+//
+
+import Foundation
+
+//To create Node property
+public class Node<T> {
+    var value: T
+
+    init(value: T){
+        self.value = value
+    }
+
+    var next: Node<T>?
+    weak var prev: Node<T>?
+}
+
+//Data Structure logics
+public class DoubleLinkedList<T> {
+    fileprivate var head: Node<T>?
+    private var tail: Node<T>?
+
+    public var isEmpty: Bool {
+        return head == nil
+    }
+
+    public var first: Node<T>? {
+        return head;
+    }
+
+    public var last: Node<T>? {
+        return tail
+    }
+
+    public func push(value: T) {
+
+        let curr = Node(value: value)
+
+        if let tailNode = tail {
+            curr.prev = tailNode
+            tailNode.next = curr
+        } else {
+            head = curr
+        }
+
+        tail = curr
+    }
+
+    public func getNode(index: Int) -> Node<T>? {
+
+        if index >= 0 {
+            var curr = head
+            var i = index
+
+            while curr != nil {
+                if i == 0 { return curr }
+                i -= 1
+                curr = curr!.next
+            }
+        }
+
+        return nil
+    }
+
+    public func getSize() -> Int{
+        var curr = head
+        var  i: Int = 0
+
+        while curr != nil {
+            i += 1
+            curr = curr!.next
+        }
+
+        return i
+    }
+
+    public func pop(curr: Node<T>) -> T {
+        let prev = curr.prev
+        let next = curr.next
+
+        if let prev = prev {
+            prev.next = next
+        } else {
+            head = next
+        }
+
+        next?.prev = prev
+
+        if next == nil {
+            tail = prev
+        }
+
+        curr.prev = nil
+        curr.next = nil
+
+        return curr.value
+    }
+
+    public func popAll() {
+        head = nil
+        tail = nil
+    }
+}
+
+
+public struct Queue<T> {
+
+    fileprivate var list = DoubleLinkedList<T>()
+
+    public var isEmpty: Bool {
+        return list.isEmpty
+    }
+
+    public mutating func enqueue(_ element: T){
+        list.push(value: element)
+    }
+
+    public mutating func dequeue() -> T? {
+        guard !list.isEmpty, let element = list.first else { return nil }
+
+        let removedElement = list.pop(curr: element)
+
+        return removedElement
+    }
+
+    public func peek() -> T? {
+        return list.first?.value
+    }
+
+    public func getSize() -> Int {
+        return list.getSize()
+    }
+
+    public func peekAt(index: Int) -> Node<T>? {
+        return list.getNode(index: index)
+    }
+
+    public func dequeueAll(){
+        list.popAll()
+    }
+
+}
+
+public class BookStoreCustomer {
+    var queueId: String
+    var bookQty: Int
+
+    init(queueId: String, bookQty: Int) {
+        self.queueId = queueId
+        self.bookQty = bookQty
+    }
+}
+
+//Main Program
+public func enqueueBuyer(){
+    print("Enter queue id: ", terminator: "")
+    let queueId: String? = readLine()
+    print("Enter book quantity to buy: ", terminator: "")
+    let bookQty: Int? = Int(readLine()!)
+
+    queue.enqueue(BookStoreCustomer(queueId: queueId!, bookQty: bookQty!))
+}
+
+public func clrScr(){
+    for _ in 1...25 {
+        print("")
+    }
+}
+
+public func separatorBar(length : Int){
+    for _ in 1...length {
+        print("=", terminator: "")
+    }
+    print("")
+}
+
+public func showQueue(){
+
+    if queue.isEmpty {
+        print("No data yet")
+    }
+    else{
+        let header: String = String(format: "| %-4s | %-12s | %-10s |", ("No" as NSString).utf8String!,("ID" as NSString).utf8String!, ("Quantity" as NSString).utf8String!)
+
+        separatorBar(length: header.count)
+        print(header)
+        separatorBar(length: header.count)
+        for i in 0 ..< queue.getSize()  {
+            let curr = queue.peekAt(index: i)
+            print(String(format: "| %-4d | %-12s | %-10d |", i+1, (curr!.value.queueId as NSString).utf8String!, curr!.value.bookQty))
+        }
+        separatorBar(length: header.count)
+    }
+
+}
+
+public func dequeueBuyer(){
+    if queue.isEmpty {
+       print("No data yet")
+   }
+   else{
+        if let buyer = queue.dequeue() {
+            print("Buyer with ID: \(buyer.queueId) served")
+        }
+    }
+}
+
+public func dequeueAllBuyer(){
+    queue.dequeueAll()
+
+    print("All Buyer served")
+}
+
+var queue = Queue<BookStoreCustomer>()
+
+//Dummy data
+queue.enqueue(BookStoreCustomer(queueId: "Q12", bookQty: 2))
+queue.enqueue(BookStoreCustomer(queueId: "Q14", bookQty: 3))
+queue.enqueue(BookStoreCustomer(queueId: "Q16", bookQty: 4))
+
+while true {
+
+    clrScr()
+    var choose: Int! = 0;
+
+    print("Buying Book Queue Program")
+    print("=====================")
+    if let nextCustomer = queue.peek() {
+        print("Next Queue ID to Serve: \(nextCustomer.queueId)")
+        print("=====================")
+    }
+    print("Menu")
+    print("1. Queue Buyer")
+    print("2. Show")
+    print("3. Serve Buyer")
+    print("4. Serve All Buyer")
+    print("5. Exit")
+
+    repeat {
+        print("Input: ", terminator: "")
+        if let str = readLine(){
+         choose = Int(str)
+        }
+    } while choose < 1 || choose > 5;
+
+    switch choose {
+        case 1:
+            enqueueBuyer()
+        case 2:
+            showQueue()
+        case 3:
+            dequeueBuyer()
+        case 4:
+            dequeueAllBuyer()
+        case 5:
+            print("Thank you for using this program :)")
+        default:
+            print("")
+    }
+
+    _ = readLine()
+
+    if choose == 5 {
+        break
+    }
+}