Merge pull request PrajaktaSathe#135 from siddhant2002/main

Code added for Reverse a LinkedList

Author: PrajaktaSathe

Programs/ReverseList.java

@@ -0,0 +1,74 @@
+// In this code a linkedlist is taken as input and the reversed form is displayed
+import java.util.*;
+public class ReverseList {
+    public static void main(String args[])
+    {
+        try (Scanner sc = new Scanner(System.in)) {
+            ListNode fresh,start=null,prev=null,ptr=null;
+            int c;
+            do
+            {
+                fresh=new ListNode();
+                System.out.println("Enter the data");
+                fresh.data=sc.nextInt();
+                if(start==null)
+                {
+                    start=fresh;
+                    // stores the starting address
+                }
+                else
+                {
+                    prev.next=fresh;
+                }
+                prev=fresh;
+                System.out.println("Press 1 to for next node initialization else press any number other than 1 to exit");
+                c=sc.nextInt();
+                // for next node initialization option is asked from the user
+            }while(c==1);
+            Solution nm=new Solution();
+            System.out.println("The original LinkedList is ");
+            for(ptr=start;ptr!=null;ptr=ptr.next)
+            {
+                System.out.print(ptr.data+" ");
+            }
+            System.out.println();
+            // displayes the original linkedlist
+            System.out.println("The reversed LinkedList is ");
+            nm.reverseList(start);
+            for(ptr=start;ptr!=null;ptr=ptr.next)
+            {
+                System.out.print(ptr.data+" ");
+            }
+            System.out.println();
+            // displays the reserved linkedlist
+        }
+    }
+}
+class Solution 
+{
+    public ListNode reverseList(ListNode start) 
+    {
+        if(start==null)
+            return null;
+            // if there is no elements in the linkedlist then it returns null
+        else
+        {
+            ListNode ptr,ptr1,ptr2;
+				for(ptr=null,ptr1=start,ptr2=start.next,ptr1.next=null;ptr2!=null;ptr2=ptr2.next,ptr1.next=ptr)
+				{
+					ptr=ptr1;
+					ptr1=ptr2;
+				}
+				start=ptr1;
+				return start;
+                // returns the start position of the linkedlist after reversing the list
+        }
+    }
+}
+// Solution class contains reverseList method which takes the start address as input and reverses the whole linkedlist
+class ListNode 
+{
+    int data;
+    ListNode next;
+}
+// ListNode class is created for linklist creation

README.md

@@ -109,7 +109,7 @@ It is very easy to contribute, you may follow these steps -
 82. [SwitchingLetters](https://github.com/PrajaktaSathe/Java/tree/main/Programs/SwitchingLetters.java) - Program that demonstrates switching letters according to given indexes.
 83. [Matrix Multiplication](https://github.com/siddhant2002/Java-1/blob/main/Programs/matrix/Matrix_Multiply.java) - Program to multiply two matrices.
 84. [Sieve of Eratosthenes](https://github.com/siddhant2002/Java-1/blob/main/Programs/Sieve_Of_Eratosthenes.java) - Program to multiply two matrices.
-
+85. [Reverse a LinkedList](https://github.com/siddhant2002/Java-1/blob/main/Programs/ReverseList.java) - Program to reverse a linkedList.
 # Contributors - 
 ## A big thank you to all our contributors!!!