leetcode-middle-of-the-linked-list

middle-of-the-linked-list

---

描述

Given a non-empty, singly linked list with head node head, return a middle node of linked list.
If there are two middle nodes, return the second middle node
Example 1:
Input: [1,2,3,4,5]
Output: Node 3 from this list (Serialization: [3,4,5])
The returned node has value 3. (The judge’s serialization of this node is [3,4,5]).
Note that we returned a ListNode object ans, such that:
ans.val = 3, ans.next.val = 4, ans.next.next.val = 5, and ans.next.next.next = NULL.
Example 2:
Input: [1,2,3,4,5,6]
Output: Node 4 from this list (Serialization: [4,5,6])
Since the list has two middle nodes with values 3 and 4, we return the second one.

---

*平分链表从中间获取后半段
solution

#Definition for singly-linked list.
class ListNode:
def init(self, x):
self.val = x
self.next = None
class Solution:
def middleNode(self, head: ‘ListNode’) -> ‘ListNode’:
if not head or not head.next:
return head
slow = fast =head
while fast.next and fast.next.next:
slow = slow.next
fast=fast.next.next
if fast.next:
return slow.next
else:
return slow