linked_list_cycle.go

package main

// Definition for singly-linked list.
type ListNode struct {
	Val  int
	Next *ListNode
}

func hasCycle(head *ListNode) bool {
	if head == nil {
		return false
	}

	slow, fast := head, head

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

		if slow == fast {
			return true
		}
	}
	return false
}