链表的中间结点-876

力扣（LeetCode） 链接：https://leetcode.cn/problems/middle-of-the-linked-list/discussion/

var middleNode = function (head) {
  let slow = head
  let fast = head
  while (fast !== null && fast.next !== null) {
    slow = slow.next
    fast = fast.next.next
  }
  return slow
}