Implementing Linked List in JAVA (Reverse without using iterator)

Question

I am trying to implement the linkedList class, adding a method reverse(int n) to reverse the linked list. For example, I have a linked list { A -> B -> C -> D -> E). When I call reverse(4), the linked list will become D-->C-->B-->A-->E.

I am trying to avoid using iterator, constructing new node and copying the data value. Does anyone have idea how to do it? I know there was a post about reversing linked list but that one is reversing the entire linked list.

Thank you so much for the help!

Just use the same principle.

Oliver Charlesworth
– Oliver Charlesworth

2015-10-31 20:31:40 +00:00
Commented Oct 31, 2015 at 20:31 — Oliver Charlesworth
– Oliver Charlesworth, Commented Oct 31, 2015 at 20:31

user4668606 · Accepted Answer · 2015-10-31 20:37:58Z

1

Since you don't provide your implementation of the LinkedList, i can only provide the general idea:
The complete list can be reversed by simply swaping the pointers to the previous node and the next node and updating the fields for the last and first node.

void reverse()
    node tmp = first
    first = last
    last = tmp

    while(tmp.next != null)
        node swap = tmp.next
        tmp.next = tmp.previous
        tmp.previous = swap

        tmp = swap

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