203. Remove Linked List Elements

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.

/**
* 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 *p=head;
if(head==NULL)return NULL;
while(head) {//因为有（1,1）1 ；（1）1 这样的数据，
if(head->val==val)
head= head->next;
else
break;
}
while(p->next){//这里是考虑的下一个节点的值，不能包含第一个节点就是要删除的，这种情况
if(p->next->val==val)
p->next=p->next->next;
else
p=p->next;
}
return head;
}
};