当下一个元素与下下个元素相同时,删除下下个元素。

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    ListNode* deleteDuplicates(ListNode* head) {
        ListNode* dummy_head=new ListNode{-1};
        dummy_head->next=head;
        auto cur=dummy_head;
        while(cur->next!=nullptr){
            while(cur->next->next && cur->next->next->val==cur->next->val){
                auto temp=cur->next->next;
                cur->next->next=temp->next;
                delete temp;
            }
            cur=cur->next;
        }
        return dummy_head->next;
    }
};