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 |