LeetCode-Easy刷题(17) Remove Duplicates from Sorted List

1->1->2

1->2

1->1->2->3->3

1->2->3

//链表指针控制 双指针
public ListNode deleteDuplicates(ListNode head) {
if(head ==null){
return head;
}
ListNode helper = new ListNode(0);
ListNode pre = helper;
pre.next = head;

while(head.next!=null){

ListNode next = head.next;
if(head.val != next.val){
pre.next.next = next;
pre = pre.next;
}
head = next;
}

if(pre.next.next!=null){
pre.next.next=null;;
}

return helper.next;
}