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 {
	// 快慢指针，快的总会追上慢的
	if head == nil || head.Next == nil {
		return false
	}
	slow, fast := head, head.Next
	for fast != slow {
        if fast == nil || fast.Next == nil {
            return false
        }
		slow = slow.Next
		fast = fast.Next.Next
	}
	return true
}