如何在不使用 Java 递归的情况下打印反向链表？

Question

I try printing a reverse linked list without recursion and reversing the linked list. How can I do that?

Questions : How to print a reverse linked list without using recursion and not reversing the list?

Requirements : No extra space, cannot reverse a linked list, cannot use recursion.

Here is the definition of the linked list Node

class Node {
  int value;
  Node next;

  public Node(int val) {
    this.value = val;
  }
}

Here is my recursion version of printReverseLinkedList:

public void printReverseList(Node head) {
    Node temp = head;
    if (temp.next != null) {
        printReverseList(temp.next);
    }
    System.out.print(temp.value);
}

Performace does not matter, because I just want to do in this way.

Answer 1

If you may neither reverse the list, nor use recursion, the only way to do this is this:

public void printReversList(Node head) {

    Node current = head; // used to search through the list
    Node last    = null; // stores the last element that we printed

    while (last != head) { // = we didn't print everything yet

        // find next element to print - it's one element before we reach "last"
        while (current.next != last) {
            current = current.next;
        }

        // Store the current element as the new last and print it
        last  = current;
        system.out.print(last.value);

        // reset current and start all over
        current = head;
    }
}

It is highly ineffective, but there is no other way I can think of.

Answer 2

How about using a Stack and then poping ? You said using another data-structure will be fine. This is not the fine code, but, should get the job done.

public void printReversList(Node head) {

    Stack<Node> stack = new Stack<>();

    while (head != null){

       stack.push(head);
       head = head.next;          
   }

   while (!stack.isEmpty()){
       System.out.println(stack.pop());
   }
}

Answer 3

you can try this:

public void printReverseList(Node head) {
            if(head == null) return;
            Node prev = null;
            Node revers = head;
            Node nex = null;

            while (revers != null){
                nex = revers.next;
                revers.next = prev;

                prev = revers;
                revers = nex;

            }
            System.out.println(prev);
        }

Answer 4

void ReversePrint(Node head) {
    // This is a "method-only" submission.
    // You only need to complete this method. 
    Stack<Node> stk=new Stack<>();

    Node temp=head;
    while(temp!=null){
        stk.push(temp);
        temp=temp.next;
    }
    while(!stk.isEmpty()){
        System.out.println(stk.pop().data);
    }
}

Answer 5

public void printReverseList(Node head) {
        Node node = head;
        List<Integer> list = new ArrayList<Integer>();
            if (head == null){
                System.out.println(head.data); 
            }
            else{
               while (node != null){
                list.add(0, node.data);
                node = node.next;
            }
            for (int item:list){
                System.out.println(item);
            }
        }
    }