python环形链表

[python]代码库

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

# 用于判断给定链表是否存在环
def hasCycle(head):
    if not head or not head.next:
        return False
    
    slow = head
    fast = head.next
    
    while slow != fast:
        if not fast or not fast.next:
            return False
        slow = slow.next
        fast = fast.next.next
    
    return True