【Leetcode】之Remove Duplicates from Sorted List II

来源：互联网发布：张大宇数据编辑：程序博客网时间：2024/06/14 18:37

一.问题描述

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

二.我的解题思路

删除链表节点的题目做得多了，说白了本题的考点就在于各种边界条件的处理。本题需要记录下duplicate number串的前一个数和后一个数。还要注意头结点也可能被删除。

测试通过的程序如下：

/** * 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) {        if(head==NULL) return NULL;        ListNode* before=NULL;ListNode* after=NULL;ListNode* res=head;        ListNode* curr=head;ListNode* next=head->next;  ListNode* pri;        while(curr && next){            while(next!=NULL && curr->val!=next->val ){                before=curr;                curr=curr->next;                next=curr->next;            }            if(next==NULL) break;             while(next!= NULL && curr->val==next->val ){                              curr=curr->next;                next=curr->next;            }                        if(next==NULL) after=NULL;            after=next;            if(before==NULL )             {res=after;curr=after;             if(after==NULL)                 return NULL;            next=curr->next;continue;                            }            before->next=after;            if(after==NULL) break;            curr=after;            next=curr->next;        }        return res;    }};

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