新增一个头节点的思想值得学习 vHead

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