删除链表中重复的结点

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) :
        val(x), next(NULL) {
    }
};
*/
class Solution {
public:
    ListNode* deleteDuplication(ListNode* pHead)
    {
        if(!pHead || !pHead->next)
            return pHead;
        
        ListNode *dummy = new ListNode(-1);
        dummy->next = pHead;
        
        ListNode *pre = dummy;
        ListNode *curr = dummy->next;
        
        while(curr && curr->next){
            if(curr->val == curr->next->val){
                while(curr->next && curr->val == curr->next->val){
                    curr = curr->next;
                }
                pre->next= curr->next;
                curr = curr->next;
            }
           else{
               pre = curr;
               curr = curr->next;
           }   
            
        }
        
        return dummy->next;
        
    }
};