question with source code added

Author: muskanmi

LinkedList/ReverseKNodes.java

@@ -0,0 +1,85 @@
+package LinkedList;
+
+public class ReverseKNodes {
+    static Node head;
+ 
+    class Node {
+ 
+        int data;
+        Node next;
+ 
+        Node(int d) {
+            data = d;
+            next = null;
+        }
+    }
+ 
+    /* Reverses alternate k nodes and
+     returns the pointer to the new head node */
+    Node kAltReverse(Node node, int k) {
+        Node current = node;
+        Node next = null, prev = null;
+        int count = 0;
+ 
+        /*1) reverse first k nodes of the linked list */
+        while (current != null && count < k) {
+            next = current.next;
+            current.next = prev;
+            prev = current;
+            current = next;
+            count++;
+        }
+ 
+        /* 2) Now head points to the kth node.  So change next
+         of head to (k+1)th node*/
+        if (node != null) {
+            node.next = current;
+        }
+ 
+        /* 3) We do not want to reverse next k nodes. So move the current
+         pointer to skip next k nodes */
+        count = 0;
+        while (count < k - 1 && current != null) {
+            current = current.next;
+            count++;
+        }
+ 
+        /* 4) Recursively call for the list starting from current->next.
+         And make rest of the list as next of first node */
+        if (current != null) {
+            current.next = kAltReverse(current.next, k);
+        }
+ 
+        /* 5) prev is new head of the input list */
+        return prev;
+    }
+ 
+    void printList(Node node) {
+        while (node != null) {
+            System.out.print(node.data + " ");
+            node = node.next;
+        }
+    }
+ 
+    void push(int newdata) {
+        Node mynode = new Node(newdata);
+        mynode.next = head;
+        head = mynode;
+    }
+ 
+    public static void main(String[] args) {
+        ReverseKNodes list = new ReverseKNodes();
+ 
+        // Creating the linkedlist
+        for (int i = 20; i > 0; i--) {
+            list.push(i);
+        }
+        System.out.println("Given Linked List :");
+        list.printList(head);
+        head = list.kAltReverse(head, 3);
+        System.out.println("");
+        System.out.println("Modified Linked List :");
+        list.printList(head);
+ 
+    }
+}