https://leetcode-cn.com/problems/middle-of-the-linked-list
func middleNode(_ head: ListNode?) -> ListNode? {
var head: ListNode? = head
var middleHead: ListNode? = head
while head?.next != nil {
head = head?.next?.next
middleHead = middleHead?.next
}
return middleHead
}
- 快慢指针