LinkedList Demonstration in Swift

LinkedList.swift

class Node {
    var value: Int
    var next: Node?
    
    init(value: Int, next: Node?) {
        self.value = value
        self.next = next
    }
    
    convenience init(value: Int) {
        self.init(value: value, next: nil)
    }
}

class LinkedList {
    var head: Node?
    var tail: Node?
    var size: Int

    init() {
        self.size = 0
    }
    
    func insertFirst(_ val: Int) {
        let node = Node(value: val)
        node.next = head
        head = node
        
        if tail == nil {
            tail = head
        }
        
        size += 1
    }
    
    func insertLast(_ val: Int) {
        while tail != nil {
            insertFirst(val)
            return
        }
        
        var node = Node(value: val)
        tail?.next = node
        tail = node
        size += 1
    }
    
    func deleteFirst() -> Int {
        let val = head?.value ?? 0
        head = head?.next
        if head == nil {
            tail = nil
        }
        
        size -= 1
        return val
    }
    
    func deleteLast() -> Int {
        if size <= 1 {
            deleteFirst()
        }
        
        var secLast = get(size - 2)
        let val = tail?.value
        tail = secLast
        tail?.next = nil
        return val ?? 0
    }
    
    func get(_ index: Int) -> Node? {
        var node = head
        for i in 0..<index {
            node = node?.next
        }
        return node
    }
   
    func display() {
        var temp = head
        while temp != nil {
            print("\(String(describing: temp!.value)) -> ", terminator: "")
            temp = temp?.next
        }
        print("@End")
    }
}

func performLinkedListOps() {
    let ll = LinkedList()
    ll.insertFirst(3)
    ll.insertFirst(5)
    ll.insertFirst(7)
    ll.insertFirst(9)
    ll.display()
    ll.insertLast(10)
    ll.display()
    ll.deleteFirst()
    ll.display()
    ll.deleteLast()
    ll.display()
    print("LL size: \(ll.size)")
}

performLinkedListOps()