LeetCode-Remove Duplicates from Sorted List II

题目：https://oj.leetcode.com/problems/remove-duplicates-from-sorted-list-ii/

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

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

源码：Java版本
算法分析：时间复杂度O(n)，空间复杂度O(1)

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