Method getMid

java/0148-sort-list.java:13–20

(ListNode head)

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;