Reversing doubly linked list in swift.

ReverseDLinkedList.swift

class Node<T> {
    var value:T
    var next: Node?
    var previous: Node?
    
    init(value: T) {
        self.value = value
        self.next = nil
        self.previous = nil
    }
}

//Reversing doubly linked list
func reverseDoublyLinkedList(head: Node<Int>) -> Node<Int>? {
    var h: Node<Int>? = head
    var temp: Node<Int>? = nil
    var current: Node<Int>? = h
    
    while current != nil {
        temp = current!.previous
        current!.previous = current!.next
        current!.next = temp
        current = current!.previous
    }
    
    if temp != nil {
        h = temp?.previous
    }
    
    return h
}

//test
let head = Node(value: 1)
let second = Node(value: 2)
let third = Node(value: 3)
let fourth = Node(value: 4)

head.next = second
second.previous = head
second.next = third
third.previous = second
third.next = fourth
fourth.previous = third