LintCode:删除列表中的元素

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
/**
* @param head a ListNode
* @param val an integer
* @return a ListNode
*/
ListNode *removeElements(ListNode *head, int val) {
// Write your code here
if(head==NULL) return head;
while(head->val==val){
head = head->next;
if(head==NULL) return NULL;
}
ListNode *p = head;
while(p->next!=NULL){
if(p->next->val == val){
p->next = p->next->next;
}
else{
p = p->next;
}
}
return head;
}
};