删除链表中等于给定值val的所有节点。

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