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;    }}