LeetCode OJ：Remove Duplicates from Sorted List II（链表去重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.

这里对于链表去重是要将有重复的链表节点全部都去掉，一个都不能留，思路还是比较简单的，跟前面的I那一题实际上差不多，代码如下所示：

 /**
  * Definition for singly-linked list.
  * struct ListNode {
  *     int val;
  *     ListNode *next;
  *     ListNode(int x) : val(x), next(NULL) {}
  * };
  */
 class Solution {
 public:
     ListNode* deleteDuplicates(ListNode* head) {
         if(!head) return NULL;
         ListNode * helper = new ListNode(INT_MAX);
         helper->next = head;
         ListNode * prev = helper;
         ListNode * curr = head;
         while(curr){
             if(curr->next && curr->val == curr->next->val){
                 ListNode * tmpNode = curr->next;
                 while(tmpNode->next && curr->val == tmpNode->next->val){
                     tmpNode = tmpNode->next;
                 }
                 prev->next = tmpNode->next;
                 curr = prev->next;
             }else{
                 prev = curr;
                 curr = curr->next;
             }
         }
         return helper->next;
     }
 };