双链表

Question

I've been trying to figure out how to reverse the order of a doubly-linked list.I've recently made an account on hackerrank and this was my 10th problem. It took me 1 hour to figure out the solution (I used pen and paper and tried many times) and finally it passed as correct. After that, I saw some answers submitted my some other folks.Their code was very small in length in comparison to mine or you think my answer is also okay. I have no one to ask to so I came here... I feel dumb when I see that.Can I improve it in future?? (forgive me if you think this is a dumb question)

    Node Reverse(Node head) {
     Node prevNode = null;
     Node NextNode = null;
     Node m = head;
     Node upComingNode = null;
     Node temp = head;
     if(head == null){
      return head;
  }
    else{
        while(temp!=null){
            NextNode = temp.next;
            temp.next = prevNode;
            m.prev = upComingNode;
            prevNode = temp;
            upComingNode = prevNode.next;
            m = temp;
            temp = NextNode;  
        }
       head = prevNode;
    }
    return head;


}

Answer 1

I am not sure what language you are working in, but to reverse a doubly linked list you, in brief, you want to swap your next and prev nodes for each node. This can be done fairly shortly and the pseudocode is below:

while(currNode != tail){
    currNode.nextNode = tempNode
    currNode.nextNode = currNode.prevNode
    currNode.prevNode = tempNode
    currNode = currNode.prevNode
}

Note that we set the next node to iterate on as the previous node, since the previous node is actually pointing to the next node now that we made the switch.