LeetCode-Easy刷题(17) Remove Duplicates from Sorted List

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.

删除排好序链表中重复的数字.返回一个数字不重复的链表

 //链表指针控制 双指针    public ListNode deleteDuplicates(ListNode head) {        if(head ==null){            return head;        }        ListNode helper = new ListNode(0);        ListNode pre = helper;        pre.next = head;        while(head.next!=null){            ListNode next = head.next;            if(head.val != next.val){                pre.next.next = next;                pre = pre.next;            }            head = next;        }        if(pre.next.next!=null){            pre.next.next=null;;        }        return helper.next;    }