82. 删除排序链表中的重复元素 II

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */


struct ListNode* deleteDuplicates(struct ListNode* head){
    struct ListNode *cur = head;
    struct ListNode dummy;
    dummy.next = head;
    struct ListNode *prev = &dummy;
    
    while (cur && cur->next) {
        
        if (cur->val == cur->next->val) {
            int val = cur->val;
            
            cur = cur->next->next;
            while (cur && cur->val == val) {
                cur = cur->next;
            }
            prev->next = cur;
        } else {
            prev = cur;
            cur = cur->next;
        }
    }

    return dummy.next;
}