"Leetcode" "Python" Linked List Cycle

Given A linked list, determine if it has a cycle in it.

Follow up:

Can you solve it without using extra space?

Idea: The stupid way is to each node and then open up a property store whether or not to visit, so walk through it can know whether there is a ring. But in order not to add extra space. Ability to set two pointers. One step at a time, and one step at a time, assuming that there is a ring two pointers will meet again. Conversely, it does not.

# Definition for singly-linked list.# class listnode:#     def __init__ (self, x): #         self.val = x#         Self.next = Nonec Lass Solution:    # @param head, a listnode    # @return a Boolea    def hascycle (self, head):        if head is none:
   
    return False        p1 = head        P2 = head while        True:            If p1.next are not None:                p1=p1.next.next                p2= P2.next                If P1 is None or P2 is none:                    return False                elif P1 = = P2:                    return True            else:                return Fa LSE        return False
   

"Leetcode" "Python" Linked List Cycle