题解 | #删除有序链表中重复的元素-II# 做题目要有自己的思路

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */
/*
1，哨兵节点
2，设置curr指向head，prev指向哨兵节点
3，while(curr && curr->next) {
    if (curr != curr->next) {
        curr和prev一起向后
    } else {
        while(curr->next && curr->val == curr->next->val) {
            curr = curr->next->Next;
        }
        prev->next = curr->next;
        curr = curr->next;
    }
 }
*/
class Solution {
public:
    /**
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    ListNode* deleteDuplicates(ListNode* head) {
        if(!head) {
            return head;
        }
        ListNode *pHead = new ListNode(head->val - 1);
        pHead->next = head;
        ListNode *prev = pHead, *curr = head, *ret = pHead;
        while(curr && curr->next) {
            if (curr->val != curr->next->val) {
                prev = prev->next;
            } else {
                while(curr->next && curr->val == curr->next->val) {
                    curr->next = curr->next->next;
                }
                prev->next = curr->next;
            }
           curr = curr->next;
        }
        return ret->next;
        // write code here
    }
};