2130. 链表最大孪生和

题目链接 2130. 链表最大孪生和
思路 链表综合题:快慢指针 + 指针翻转
题解链接 官方题解
关键点 while fast.next and fast.next.next: ...
时间复杂度 O(n)
空间复杂度 O(1)

代码实现:

class Solution:
def pairSum(self, head: Optional[ListNode]) -> int:
if head is None:
return 0
first = self.halfList(head)
second = self.reverseList(first.next)
answer = 0
while second:
answer = max(answer, head.val + second.val)
head = head.next
second = second.next
return answer
def halfList(self, head):
slow = fast = head
while fast.next and fast.next.next:
fast = fast.next.next
slow = slow.next
return slow
def reverseList(self, head):
previous = None
current = head
while current:
next_node = current.next
current.next = previous
previous = current
current = next_node
return previous
posted @   WrRan  阅读(2)  评论(0编辑  收藏  举报
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