package main
import . "nc_tools"
/*
 * type ListNode struct{
 *   Val int
 *   Next *ListNode
 * }
 */

/**
 * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
 *
 * 
 * @param head ListNode类 
 * @return ListNode类
*/
func middleNode( head *ListNode ) *ListNode {
    slow, fast := head, head
    for fast != nil {
        if fast.Next == nil {
            break
        }
        fast = fast.Next.Next
        slow = slow.Next
    }
    return slow
}