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