LeetCode | Remove Duplicates from Sorted List II

https://leetcode.com/problems/remove-duplicates-from-sorted-list-ii/

不断定位出重复的段，然后删除这段。C++须要手动删除链表节点。

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if (!head || !head->next) return head;
        
        ListNode dummy(0); dummy.next = head;
        ListNode *cur = &dummy, *start = head, *end = start; // start和end指针分别指向duplicates的开始和结束
        while (cur) {
            while (end && end->next && end->next->val == start->val) {
                end = end->next;
            }
            if (end != start) {
                cur->next = end->next;
                // delete the duplicates
                while (start != end) {
                    ListNode *next = start->next;
                    delete start;
                    start = next;
                }
                delete start;
            } else { cur = cur->next; }
            if (cur) { start = cur->next; end = start; }
        }
        return dummy.next;
    }
};