题解 | #判断链表中是否有环#

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

/**
 * 
 * @param head ListNode类 
 * @return bool布尔型
*/
func hasCycle( head *ListNode ) bool {
   
   if head == nil {
        return false 
   }
   fast := head
   slow := head

   for i := 0; ; i++ {
        if fast == nil || fast.Next == nil {
            return false 
        }
        fast = fast.Next.Next
        slow = slow.Next
        if fast == slow {
            return true
        }
   }
}