删除排序链表中的重复元素

题目链接：https://leetcode-cn.com/problems/remove-duplicates-from-sorted-list/

题解：双指针

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if(head == null) return null;

        ListNode dummy = new ListNode(-1);
        dummy.next = head;
        ListNode l = dummy.next,r = l.next;

        while(r != null){
            if(l.val == r.val){
                while(r != null && l.val == r.val){
                    r = r.next;
                }
                l.next = r;
                l = r;
                r = l==null? null:l.next; 
            }else{
                l = l.next;
                r = r.next;
            }
        }
        return dummy.next;
    }
}

题目的版本2：https://www.cnblogs.com/cstdio1/p/13537961.html