Merge pull request neetcode-gh#2479 from Anukriti167/patch-4

Update 0148-sort-list.java

java/0148-sort-list.java

@@ -1,3 +1,64 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ * int val;
+ * ListNode next;
+ * ListNode() {}
+ * ListNode(int val) { this.val = val; }
+ * ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+ // Merge Sort Implementation
+ public ListNode getMid(ListNode head){
+ ListNode slow=head, fast=head.next;
+ while(fast != null && fast.next != null){
+ fast = fast.next.next;
+ slow = slow.next;
+ }
+ return slow;
+ }
+ public ListNode merge(ListNode left, ListNode right){
+ ListNode dummy = new ListNode();
+ ListNode tail = dummy;
+
+ while(left != null && right != null){
+ if(left.val < right.val){
+ tail.next = left;
+ left = left.next;
+ }else{
+ tail.next = right;
+ right = right.next;
+ }
+ tail = tail.next;
+ }
+ if(left != null){
+ tail.next = left;
+ }
+ if(right != null){
+ tail.next = right;
+ }
+ return dummy.next;
+ }
+ public ListNode sortList(ListNode head) {
+ if(head == null || head.next == null){
+ return head;
+ }
+
+ // Split the list in 2 halfs
+ ListNode left = head;
+ ListNode right = getMid(head);
+ ListNode tmp = right.next;
+ right.next = null;
+ right = tmp;
+
+ left = sortList(left);
+ right = sortList(right);
+ return merge(left, right);
+ }
+}
+
+// Using a Heap to sort the list
 class Solution {
  public ListNode sortList(ListNode head) {
  if(head == null || head.next == null){