Remove Linked List Elements

基础题

注意要bug free看清楚细节得

public class Solution {
    public ListNode removeElements(ListNode head, int val) {
        if(head==null ) return null;
        ListNode h = new ListNode(-1);
        h.next = head;
        ListNode n = head, pre = h;
        while(n!=null){
            if(n.val==val){
                pre.next = n.next;
            }else{
            pre = pre.next;  
            }
            n =pre.next;
        }
        return h.next;
    }
}