Remove Duplicates from Sorted List

Given a sorted linked list, delete all duplicates such that each element appear onlyonce.

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

思路： 判断是否重复，就需要用双指针，利用pre和cur两个指针来判断。如果相等，就代表有重复，那么用delete的操作来delete重复点，那么就是pre.next = cur.next;来delete掉cur的点。如果不相等，那么pre进行移动。pre = cur;

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { val = x; } * } */public class Solution {    public ListNode deleteDuplicates(ListNode head) {        if(head == null || head.next == null) {            return head;        }        ListNode dump = new ListNode(0);        dump.next = head;        ListNode pre = head;        while(pre!=null && pre.next!=null){            ListNode cur = pre.next;            if(pre.val == cur.val){                pre.next = cur.next;            } else {                pre = cur;            }        }        return dump.next;    }}