LeetCode刷题笔记（链表）：remove-duplicates-from-sorted-list-ii

偏执的太偏执、 2022-06-01 01:57 99阅读 0赞

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*  **转载请注明作者和出处：[http://blog.csdn.net/u011475210][http_blog.csdn.net_u011475210]**
 *  **代码地址：[https://github.com/WordZzzz/Note/tree/master/LeetCode][https_github.com_WordZzzz_Note_tree_master_LeetCode]**
 *  **刷题平台：[https://www.nowcoder.com/ta/leetcode][https_www.nowcoder.com_ta_leetcode]**
 *  **题  库：Leetcode经典编程题**
 *  **编  者：WordZzzz**

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*   *  题目描述
     *  解题思路
     *  C版代码实现

## 题目描述 ##

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

For example,  
Given1->2->3->3->4->4->5, return1->2->5.  
Given1->1->1->2->3, return2->3.

## 解题思路 ##

因为第一个元素就有可能是重复节点，所以我们需要新建一个头节点指针，这一点在之前的几道题都有提到过。然后设置快慢指针，fast从head开始遍历，slow总是比fast慢一步；如果fast当前元素和它的下一个元素不相等，则更新slow、fast；否则，遍历重复元素，直到fast落到最后一个重复元素上，然后更新slow（跳过重复节点，直接指向fast的下一个节点）、fast。

## C++版代码实现 ##

/**
     * 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 || head->next == NULL)
                return head;
    
            ListNode *dummy = new ListNode(0);
            dummy->next = head;
            ListNode *fast = head;
            ListNode *slow = dummy;
            while(fast != NULL && fast->next != NULL){
                if(fast->next->val != fast->val)
                    //更新slow
                    slow = fast;
                else{
                    //遍历重复的元素，fast落到重复元素的最后一个元素上。
                    while(fast->next && fast->next->val == fast->val)
                        fast = fast->next;
                    //删掉slow和fast之间的元素
                    slow->next = fast->next;
                }
                //更新fast
                fast = fast->next;
            }
            return dummy->next;
        }
    };

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[http_blog.csdn.net_u011475210]: http://blog.csdn.net/u011475210
[https_github.com_WordZzzz_Note_tree_master_LeetCode]: https://github.com/WordZzzz/Note/tree/master/LeetCode
[https_www.nowcoder.com_ta_leetcode]: https://www.nowcoder.com/ta/leetcode