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  1. Reverse a doubly linked list
  2. Discussions

Reverse a doubly linked list

  • lf963
     + 0 comments

    Java

    Iterative

    public static DoublyLinkedListNode reverse(DoublyLinkedListNode llist) {
	DoublyLinkedListNode newHead = null;
	while(llist != null){
		DoublyLinkedListNode next = llist.next;
		llist.next = newHead;
		llist.prev = next;
		newHead = llist;
		llist = next;
	}
	return newHead;
}

    Recursive:

    public static DoublyLinkedListNode reverse(DoublyLinkedListNode llist) {
	return helper(null, llist);
}

private static DoublyLinkedListNode helper(DoublyLinkedListNode prev, DoublyLinkedListNode node){
	if(node == null)
		return prev;
	DoublyLinkedListNode next = node.next;
	node.next = prev;
	node.prev = next;
	return helper(node, next);
}