[LeetCode] Remove Linked List Elements 移除链表元素

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.

这道移除链表元素是链表的基本操作之一，没有太大的难度，就是考察了基本的链表遍历和设置指针的知识点，我们只需定义几个辅助指针，然后遍历原链表，遇到与给定值相同的元素，将该元素的前后连个节点连接起来，然后删除该元素即可，要注意的是还是需要在链表开头加上一个dummy node，具体实现参见代码如下：

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* removeElements(ListNode* head, int val) {
ListNode *dummy = new ListNode(-1);
dummy->next = head;
ListNode *pre = dummy, *cur = head;
while (cur) {
if (cur->val == val) {
ListNode *tmp = cur;
pre->next = cur->next;
cur = cur->next;
delete tmp;
} else {
cur = cur->next;
pre = pre->next;
}
}
return dummy->next;
}
};

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