Loop in Linked List With Swift

Loop_LinkedList.swift

import Foundation

class LinkedList<T> {
    
    class Node<T> {
        var value: T
        var next: Node?
        init (value: T){
            self.value = value
        }
    }
    
    private var head: LinkedList.Node<T>?
    
    var isEmpty: Bool {
        return head == nil
    }
    
    var first: LinkedList.Node<T>? {
        return head
    }
    
    var last: LinkedList.Node<T>? {
        guard var node = head else {
            return nil
        }
        while let next = node.next {
            node = next
        }
        return node
    }
    
    func append(value:T) {
        let newNode = Node(value: value)
        if let lastNode = last {
            lastNode.next = newNode
        } else {
            head = newNode
        }
    }
}

extension LinkedList where T: Equatable {
    var isLoopedList: Bool {
        guard var node = head else {return false}
        var xs = [T](arrayLiteral: node.value)
        while let next = node.next {
            if xs.contains(next.value) {
                return true
            }
            xs.append(next.value)
            node = next
        }
        return false
    }
}

//TODO: add Floyd's cycle detection algorithm


//test
let list = LinkedList<String>()

let string1 = "Hello"
let string2 = "World"

list.append(value: string1)
list.append(value: string2)
list.isLoopedList

list.append(value: string1)
list.isLoopedList
list.append(value: string2)
list.isLoopedList