Problem statement: You have given a pointer to the head node of a linked list, the task is to reverse the linked list.
Example: 1->2->3->4->5->null
Output: 5->4->3->2->1->null
Prerequisite:
In this tutorial, we are writing Java program to reverse linked list. You can also check C++ code to reverse linked list.
import java.util.*;
class Main {
public static class ListNode {
int val = 0;
ListNode next = null;
ListNode(int val) {
this.val = val;
}
}
// we will get each node data and from beginning to last
// and swap them with each other
public static ListNode reverse(ListNode head) {
ListNode n = head;
int size = 0;
while (n != null) {
size ++;
n = n.next;
}
int i = 0, j = size - 1;
while (i < j) {
ListNode a = getNode(i, head);
ListNode b = getNode(j, head);
int temp = a.val;
a.val = b.val;
b.val = temp;
i++;
j--;
}
return head;;
}
private static ListNode getNode(int indx, ListNode head) {
ListNode n = head;
if (indx == 0)
return head;
for (int i = 0; i < indx; i++) {
n = n.next;
}
return n;
}
public static void main(String[] args) {
Scanner scn = new Scanner(System.in);
int n = scn.nextInt();
ListNode dummy = new ListNode(-1);
ListNode prev = dummy;
while (n-- > 0) {
prev.next = new ListNode(scn.nextInt());
prev = prev.next;
}
ListNode head = reverse(dummy.next);
while (head != null) {
System.out.print(head.val + " ");
head = head.next;
}
}
}
As we are using Java basics syntax to implement this logic, it will work for any Java versions like Java 8, Java 12,…
You can implement this logic in C/C++ and python as well.
This is all about this tutorial to reverse a Linked List In JAVA. If you have any questions or point to discuss, let me know in the comment.
I am Sachin Sharma a complete JAVA geek and I also have good knowledge of Python, C, C++, and front-end development. I am a 5-star gold coder on Hckerrank in JAVA, Python, C++, and DSA. I am eager to share my coding knowledge to help people.