136、只出现一次的数字
class Solution:
def singleNumber(self, nums: List[int]) -> int:
a = 0
for num in nums:
a = a ^ num
return a
141、环形链表
Definition for singly-linked list.
# class ListNode:
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution:
def hasCycle(self, head: ListNode) -> bool:
while head:
if head.val == 'bjfuvth':
return True
else:
head.val = 'bjfuvth'
head = head.next
return False
142、环形链表2
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution:
def detectCycle(self, head: ListNode) -> ListNode:
fast = slow = head
while fast and fast.next:
fast = fast.next.next
slow = slow.next
if fast == slow:
while head != slow:
head = head.next
slow = slow.next
return head
return None
