reverse of a linked list

Question

Anonymous · Accepted Answer

using recursion


class Node
{
    int data;
    Node next;
    Node(int data)
    {
        this.data=data;
        next=null;
    }
}
class ReverseLLRecursion
{
    static Node reverse(Node head)
    {
        if(head.next==null)
            return head;
        reverse(head.next).next=head;
        head.next=null;
        return head;
    }
    public static void main(String[] st)
    {
        Node n1=new Node(1);
        Node n2=new Node(2);
        Node n3=new Node(3);
        Node n4=new Node(4);
        
        n1.next=n2;
        n2.next=n3;
        n3.next=n4;
        
        reverse(n1);
        Node tra=n4;
        while(tra!=null)
        {
            System.out.println(tra.data+", ");
            tra=tra.next;
        }
    }
}

Mohamed · Answer

Given a LinkedList of Node (val, next), below is an in-place reverse function:

// Class: Node
var Node = function(val) {
    this.val = val;
    this.next = null;
};

// Assuming there is a linked-list with 2 nodes
var reverse = function(linkedList) {
        var previous = linkedList.head,
            current = previous.next,
            next
        ;
      
        previous.next = null;
      
        while(current != null) {
            next = current.next;
            current.next = previous;
            previous = current;
            current = next;
        }
      
        linkedList.head = previous;
};

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