Compiled Merge Sort Code

12_LinkedList.java/MergeSort.java

@@ -1,16 +1,93 @@
-import java.util.LinkedList;
-public class MergeSort {
-    public static void mergeSort(LinkedList<Integer> ll) {
-
-
+import java.util.*;
+public class D25_MergeSortLL {
+    public static class Node {
+        int data;
+        Node next;
+        public Node(int data) {
+            this.data = data;
+            this.next = null;
+        }
     }
-    public static void main(String args[]) {
-        LinkedList<Integer> ll = new LinkedList<>();
-        ll.addLast(4);
-        ll.addLast(3);
-        ll.addLast(2);
-        ll.addLast(1);
-
-        System.out.println(ll); 
+    public static Node head;
+    public static Node tail;
+    public  Node FindMiddle(Node head) {
+        Node slow = head;
+        Node fast = head.next;
+        while (fast != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+        }
+        return slow;
+    }
+    public  Node merge(Node head1, Node head2) {
+        Node mergedLL = new Node(-1);
+        Node temp = mergedLL;
+        while (head1 != null && head2 != null) {
+            if (head1.data >= head2.data) {
+                temp.next = head2;
+                head2 = head2.next;
+                temp = temp.next;
+            } else {
+                temp.next = head1;
+                head1 = head1.next;
+                temp = temp.next;
+            }
+        }
+        while (head1 != null) {
+            temp.next = head1;
+            head1 = head1.next;
+            temp = temp.next;
+        }
+        while (head2 != null) {
+            temp.next = head2;
+            head2 = head2.next;
+            temp = temp.next;
+        }
+        return mergedLL.next;
+    }
+    public Node mergeSort(Node head) {
+        if (head == null || head.next == null) {
+            return head;
+        }
+        Node mid = FindMiddle(head);
+        Node rightHead = mid.next;
+        mid.next=null;
+        Node newleft = mergeSort(head);
+        Node newRight = mergeSort(rightHead);
+        return merge(newleft, newRight);
+    }
+    public void addFirst(int data) {
+        Node newNode = new Node(data);
+        if (head == null) {
+            head = newNode;
+        }else{
+        newNode.next = head;
+        head = newNode;
+}
+    }
+    public void print_LL() {
+        if (head == null) {
+            System.out.println("Linked List is empty");
+            return;
+        }
+        Node temp = head;
+        while (temp != null) {
+            System.out.print(temp.data + "=>");
+            temp = temp.next;
+        }
+        System.out.println("null");
+    }
+    public static void main(String[] args) {
+        D25_MergeSortLL LL =new D25_MergeSortLL();
+        LL.addFirst(1);
+        LL.addFirst(2);
+        LL.addFirst(3);
+        LL.addFirst(4);
+        LL.addFirst(5);
+        System.out.println("UNSORTED LINKED LIST");
+        LL.print_LL();
+        LL.head=LL.mergeSort(head);
+        System.out.println("SORTED LINKED LIST - AFTER APPLYING MERGE SORT");
+        LL.print_LL();
     }
 }