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  1. Reverse a doubly linked list
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Reverse a doubly linked list

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  • 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);
}

  • fadelabdelhamid1
     + 0 comments

    This and "reverse a linked list" code is bugged from the beggining in Java 8 (the only Java that has autocomplete), is there any fu__ing checking in this website ?

  • vadym_usatiuk
     + 0 comments

    Java 15 O(n)

    public static DoublyLinkedListNode reverse(DoublyLinkedListNode llist) {
        DoublyLinkedListNode current = llist;
        DoublyLinkedListNode prev = null;

        while (current != null) {
            DoublyLinkedListNode nextNode = current.next;
            current.next = prev;
            current.prev = nextNode; // swap prev and next pointers
            prev = current;
            current = nextNode;
        }

        //prev points to the new head of the reversed list
        return prev;
    }

  • qqsergiu
     + 0 comments

    Kotlin code is bugged and cannot be solved in this language!

  • filip_kujikis
     + 0 comments

    Bugs in the output code in Kotlin make it impossible to complete this and other exercises. Why is the output code locked from editing?!?!