LeetCode 203. Remove Linked List Elements

题目链接：https://leetcode.com/problems/remove-linked-list-elements/

题目描述：

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.

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* 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) {
if (head == NULL)
return head;
while (head->val == val)
{
head = head->next;
if (head == NULL)
return head;
}
/*以上两部分可以合到一起
while (head!=NULL&&head->val == val)//注意：两项顺序不能倒过来，当&&前面的为假时不会编译后面的！！！
{
head = head->next;
}
if(head==NULL)
return head;
*/
ListNode* p = head->next;
ListNode* q = head;
while (p != NULL)
{
if (p->val == val)
{
q->next = p->next;
p = p->next;
}
else
{
p = p->next;
q = q->next;
}

}
return head;
}
};

注：在vs测试时，ListNode* test=new ListNode(1);调用构造函数进行初始化