LeetCode 203. Remove Linked List Elements

Posted 2020-10-20 皇家大鹏鹏

Remove all elements from a linked list of integers that have value val.

Example
Given: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6
Return: 1 --> 2 --> 3 --> 4 --> 5

Credits:
Special thanks to @mithmatt for adding this problem and creating all test cases.

 

要求删除给定数值的节点，题目不难，老方法，引入虚拟头结点避免使用二重指针，遍历是一定要考虑指针为空的情况，否则不要去访问其next域，最后记得释放节点

代码如下：

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode* removeElements(ListNode* head, int val) {
12         ListNode *dummy = new ListNode(-1), *pre = dummy;
13         dummy->next = head;
14         while (pre)
15         {
16             if (pre->next && pre->next->val == val)
17             {
18                 ListNode *t = pre->next;
19                 pre->next = t->next;
20                 delete t;
21             }
22             else
23                 pre = pre->next;
24         }
25         return dummy->next;
26         
27     }
28 };

时间复杂度：O(N)

空间复杂度：O(1)

 

参考：https://leetcode.com/problems/remove-linked-list-elements/discuss/57308/