Reverse a Linked List – Iterative Way, Solution with example

Problem Statement

How to reverse a linked list in the most optimized time complexity in an iterative way?

Solution: Iterative Method

Code / Pseudo code / Method

public Node reverseLikedList(Node head) {
 Node prev = null;
 Node current = head;
 Node next = null;
 while (current != null) {
  next = current.next;
  current.next = prev;
  prev = current;
  current = next;
 }
 head = prev;
 return head;
}

Following is a clear and intuitive explanation that will help in understanding the iterative way of reversing a linked list.

Still unclear, check out the following GeeksForGeeks link where it is explained in Java code.

Source Code in Java

package com.nishant.linkedlist;
public class ReverseLinkedlist {
	public static void main(String[] args) {
		Linkedlist<String> ll = new Linkedlist<>();
		ll.add("Debi");
		ll.add("Kally");
		ll.add("Nishant");
		ll.add("Palak");
		ll.add("Priyanka");
		ll.add("Srabari");
		
		System.out.println("Current state of the list: ");
		ll.printList();
		
		System.out.println("\nState of the list after the reverse method is called: ");
		reverseList(ll);
		ll.printList();
	}

/*
               p  c     n
 null<-- 1 <-- 2  3 --> 4 --> 5 --> null
	c 
	p =  2
*/
	private static void reverseList(Linkedlist<String> ll) {
		Node<String> current = ll.getHead();
		Node<String> next = null;
		Node<String> prev = null;
		
		while(current != null){
			next = current.getNext(); // 2
			current.setNext(prev);    // 
			prev = current;           // 1
			current = next;           // 2
		}
		ll.setHead(prev);
	}
}

Check out the GeeksforGeeks link. It has explained the process in an animated way and the code is available in all languages – C, C++, Java, Python & C#.

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