leetcode：Remove Duplicates from Sorted List II

移除链表中重复的元素

/**
* 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){
ListNode th = new ListNode(0);
th.next = head;
ListNode pre = th;
ListNode next = head;
while(next != null && next.next != null){
if(next.val == next.next.val){
int val = next.val;
while(next != null && next.val == val){
next = next.next;
}
pre.next = next;
}
else {
pre = next;
next = next.next;
}
}
pre.next = next;
head = th.next;

}
return head;
}
}