203. 删除链表中的节点

/**
 * 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 *pre=head;
        ListNode *p=head;
        while(p)
        {
            if (p->val==val)
            {
                     p=p->next;pre->next=p;
            }
            else
                p=p->next;pre=p;
        }
            return head;
    }
};