0142. 环形链表 II

[giscus[bot]]

0142. 环形链表 II | 算法通关手册

https://algo.itcharge.cn/solutions/0100-0199/linked-list-cycle-ii/

[zhuoyuechen]

用哈希表理解起来简单粗暴一点。

class Solution:
    def detectCycle(self, head: Optional[ListNode]) -> Optional[ListNode]:
        Ss = set()
        if not head or not head.next:
            return None
        cur = head
        while cur:
            if cur in Ss:
                return cur
            else:
                Ss.add(cur)
            cur = cur.next
        return None