876. Middle of the Linked List

题目

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.

Note:

The number of nodes in the given list will be between 1 and 100.

题目大意

输出链表中间结点。这题在前面题目中反复出现了很多次了。

如果链表长度是奇数，输出中间结点是中间结点。如果链表长度是双数，输出中间结点是中位数后面的那个结点。

解题思路

这道题有一个很简单的做法，用 2 个指针只遍历一次就可以找到中间节点。一个指针每次移动 2 步，另外一个指针每次移动 1 步，当快的指针走到终点的时候，慢的指针就是中间节点。