動機
複習linked list找中點
Problem
Given the head
of a singly linked list, return the middle node of the linked list.
If there are two middle nodes, return the second middle node.
Example 1:
Input: head = [1,2,3,4,5]Output: [3,4,5]Explanation: The middle node of the list is node 3.
Example 2:
Input: head = [1,2,3,4,5,6]Output: [4,5,6]Explanation: Since the list has two middle nodes with values 3 and 4, we return the second one.
Constraints:
- The number of nodes in the list is in the range
[1, 100]
. 1 <= Node.val <= 100
Sol
class Solution:
def middleNode(self, head: ListNode) -> ListNode:
end = head
while end.next and end.next.next:
head, end = head.next, end.next.next
if end.next:
return head.next
else:
return head