LeetCode OJ：Remove Duplicates from Sorted List （排好序的链表去重）

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.

简单的链表去重而已啊，遍历一边就实现了：

 class Solution {
 public:
     ListNode* deleteDuplicates(ListNode* head) {
         ListNode * p = head;
         if(p == NULL || p->next == NULL)
             return p;
         ListNode * prev = p;
         p = p->next;
         while(p!=NULL){
             if(p->val == prev->val){
                 prev->next = p->next;
             }else{
                 prev = p;
             }
             p = p->next;
         }
         return head;
     }
 };

下面这个实际上比上面那个要快一点，上面那个是遇到一个删掉一个，这个是遇到一连串相同的就一起删掉，java写的，runtime比上面又不小的提高，代码如下：

 /**
  * Definition for singly-linked list.
  * public class ListNode {
  *     int val;
  *     ListNode next;
  *     ListNode(int x) { val = x; }
  * }
  */
 public class Solution {
     public ListNode deleteDuplicates(ListNode head) {
         if(head == null) return null;
         ListNode helper = new ListNode(-1);
         helper.next = head;
         ListNode p = head;
         while(p.next!=null){
             if(p.val == p.next.val){
                 ListNode tmp = p.next;
                 while(tmp.next != null){
                     if(tmp.next.val == tmp.val){
                         tmp = tmp.next;
                     }else
                         break;//找到最后一个和前面相同的节点
                 }
                 p.next = tmp.next;
                 tmp.next = null;
             }else{
                 p = p.next;
             }
         }
         return helper.next;
     }
 }