题目 代码实现
/** * Definition for singly-linked list. * type ListNode struct { * Val int * Next *ListNode * } */ func hasCycle(head *ListNode) bool { fast, slow := head, head for slow != nil && fast != nil && fast.Next != nil { fast = fast.Next.Next slow = slow.Next if fast == slow { return true } } return false } /* func hasCycle(head *ListNode) bool { fast, slow := head, head for { if fast == nil || fast.Next == nil { return false // 无环 } fast = fast.Next.Next slow = slow.Next if fast == slow { return true } } } */解题思路：使用快慢指针（slow一次走一步，fast一次走两步）。如果不含有环，fast最终会遇到 nil，说明链表不含环；如果含有环，fast最终会超slow一圈，和slow相遇，说明链表含有环。
