删除链表中重复的结点

class Solution {
public:
    ListNode* deleteDuplication(ListNode* pHead)
    {
     if(pHead == NULL || pHead->next == NULL)
         return pHead;
     ListNode *head = NULL, *pb = pHead, *pe = pHead->next, *pre = head;
     while(pb && pe)
         {
         while(pe && pb->val == pe->val)
             {
              pe = pe->next;
              if(!pe)
                  {
                  if(pre)
                  pre->next = NULL;
                  return head;
              }
              else if(pb->val != pe->val)
                  {
                     pb = pe;
                     pe = pe->next;
                   //  if(!pe)
                      //   return head;
                  }
             }
           if(pre != NULL)
               {
                pre->next = pb;
                pre = pb;
                pb = pe;
                if(pe)
                pe =pe->next;
               }
         else 
         {
             head = pb;
             pre = head;
             pb = pe;
             if(pe)
             pe = pe->next;
             
         }
         
         }
        return head;
    }
};