[Leetcode] Remove Duplicates from Sorted List (Java)

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.

删除重复值节点，使每个元素只出现一次

public class Solution {    public ListNode deleteDuplicates(ListNode head) {    if(head==null)return null;ListNode res = new ListNode(-1);res.next = head;ListNode pre = head;int tmp = head.val;head=head.next;while(head!=null){if(tmp==head.val){pre.next=head.next;}else {pre=head;tmp=head.val;}head=head.next;}return res.next;            }}