0876-middle-of-the-linked-list.go

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func middleNode(head *ListNode) *ListNode {
	if head == nil || head.Next == nil {
		return head
	}

	slow, fast := head, head

	for fast != nil && fast.Next != nil {
		slow, fast = slow.Next, fast.Next.Next
	}

	return slow
}