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/
