技術標籤：資料結構與演算法

題目：判斷連結串列是否有環

//環形連結串列


//雜湊表
func hasCycle(head *ListNode) bool {
    seen := map[*ListNode]struct{}{}
    for head != nil {
        if _, ok := seen[head]; ok {
            return true
        }

        //標記該節點已被訪問
        seen[head] = struct{}{}
        head = head.Next
    }

    return false
}

//快慢指標
func hasCycle(head *ListNode) bool {
    if head == nil || head.Next == nil {
        return false
    }

    slow, fast := head, head.Next
    for fast != slow {
        if fast == nil || fast.Next == nil {
            return false
        }
        //慢指標一次移動2步
        slow = slow.Next
        //快指標一次移動2步
        fast = fast.Next.Next
    }

    return true
}
 

連結：https://leetcode-cn.com/problems/linked-list-cycle/solution/huan-xing-lian-biao-by-leetcode-solution/