题解 | #删除有序链表中重复的元素-II#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *  ListNode(int x): val(x), next(nullptr) {};
 * };
 */

class Solution {
public:
    /**
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    ListNode* deleteDuplicates(ListNode* head) {
        // write code here
        ListNode* hail = new ListNode(0);
        hail->next = head;
        
        ListNode* pre = hail;
        ListNode* cur = head;
        int cur_val = cur->val;
        
        while(cur != nullptr){
            if(cur->next == nullptr || (cur->next && cur->next->val != cur_val)){
                pre->next = cur;
                pre = cur;
                cur = cur->next;
                cur_val = cur->val;
            }
            else{
                while(cur != nullptr && cur->val == cur_val){
                    cur = cur->next;
                }
                cur_val = cur->val;
            }
        }
        pre->next = nullptr;
        return hail->next;
    }
};