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:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    ListNode* deleteDuplicates(ListNode* head) {
        auto Rm = [&head](auto p) {
            if(not p) return p;
            if(not p->next) return p->next;

            p->next = p->next->next;
            return p->next;
        };

        auto fake_head = std::make_unique<ListNode>(0);
        fake_head->next = head;
        auto valid = fake_head.get();
        while(valid->next) {
            auto a = valid->next, b = valid->next;
            for(; b and b->val == a->val; b = b -> next);
            if(a->next == b) {
                valid = a;
            } else {
                valid->next = b;
            }
        }
        return fake_head -> next;
    }
};