Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

Example 1:

Input: 1->2->3->3->4->4->5Output: 1->2->5

Example 2:

Input: 1->1->1->2->3Output: 2->3

难度：medium

题目：给出一排序链表，删除所有重复结点，只保留原链表中不重复的结点。

思路：双指针遍历

Runtime: 0 ms, faster than 100.00% of Java online submissions for Remove Duplicates from Sorted List II.

/** * 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 (null == head) {            return head;        }                ListNode dummyHead = new ListNode(0);        dummyHead.next = head;        ListNode prev = dummyHead, ptr = head;        while (ptr != null && ptr.next != null) {            if (ptr.val == ptr.next.val) {                while (ptr.next != null && ptr.val == ptr.next.val) {                    ptr = ptr.next;                }                prev.next = ptr.next;                ptr = prev;            }             prev = ptr;            ptr = ptr.next;        }                return dummyHead.next;    }}