https://leetcode.com/problems/remove-duplicates-from-sorted-list/description/
Given a sorted linked list, delete all duplicates such that each element appear only once.

For example,
Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.

 1 public ListNode deleteDuplicates(ListNode head) {
 
 2         if (head == null || head.next == null) return head ;
 3         ListNode curr = head ;
 4         /*
 5         * 重點體會跳過去是什麽意思 CURR =HEAD 然後改變 CURR.NEXT HEAD.next 也是會被變化的
 6         * */
 7         /*
 8         *  1-1-1-1-2-2-3
 9         *  c--->
10         *   ---->
11         *   ------->
 
12         *          c
13         *  h------->
14         * */
15         while(curr.next!=null){
16             if (curr.val == curr.next.val){
17                 curr.next = curr.next.next ;
18             } else {
19                 curr = curr.next ;
20             }
21         }
22         return
 
 head ;
23     }

LC_83. Remove Duplicates from Sorted List