82.删除排序链表中的重复元素-ii.cpp

/*
 * @lc app=leetcode.cn id=82 lang=cpp
 *
 * [82] 删除排序链表中的重复元素 II
 *
 * https://leetcode-cn.com/problems/remove-duplicates-from-sorted-list-ii/description/
 *
 * algorithms
 * Medium (46.69%)
 * Likes:    240
 * Dislikes: 0
 * Total Accepted:    38.7K
 * Total Submissions: 82.5K
 * Testcase Example:  '[1,2,3,3,4,4,5]'
 *
 * 给定一个排序链表，删除所有含有重复数字的节点，只保留原始链表中 没有重复出现 的数字。
 * 
 * 示例 1:
 * 
 * 输入: 1->2->3->3->4->4->5
 * 输出: 1->2->5
 * 
 * 
 * 示例 2:
 * 
 * 输入: 1->1->1->2->3
 * 输出: 2->3
 * 
 */

// @lc code=start
/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        ListNode* ret = new ListNode(0), *p=head;
        ListNode* tail = ret;
        ListNode* pre = head;
        bool dup = false;
        
        while(p!=NULL){
            cout<<p->val<<endl;
            if(p->next!=NULL && p->next->val == p->val){
                pre = p;
                p = p->next->next;
                dup = true;
            }else if(dup && p->val == pre->val){
                p = p->next;
            }else{
                pre = p;
                tail->next = p;
                tail = p;
                p = p->next;
                dup = false;
            }
        }
        tail->next = NULL;
        return ret->next;
    }
};
// @lc code=end