leetcode 876 链表的中间节点

题目
快慢指针：

class Solution {
    public ListNode middleNode(ListNode head) {
        ListNode pquick=head;
        ListNode pslow=head;
        while(pquick!=null&&pquick.next!=null){
            pslow=pslow.next;
            pquick=pquick.next.next;
        }
        return pslow;
    }
}

迭代：

class Solution {
    public ListNode middleNode(ListNode head) {
        int length=0;
        ListNode dummy=new ListNode(0);
        dummy.next=head;
        ListNode p=dummy;

        while(p.next!=null){
            length++;
            p=p.next;
        }
        int mid=length/2+1;
        p=dummy;
        while(mid>0){
                p=p.next;
                mid--;
        }
            return p;

    }
}