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: Node3fromthislist (Serialization: [3,4,5]) Thereturnednodehasvalue3. (Thejudge's serialization of this node is [3,4,5]). NotethatwereturnedaListNodeobjectans, suchthat: ans.val=3, ans.next.val=4, ans.next.next.val=5, andans.next.next.next=NULL.Example 2:
Input: [1,2,3,4,5,6] Output: Node4fromthislist (Serialization: [4,5,6]) Sincethelisthastwomiddlenodeswithvalues3and4, wereturnthesecondone.Note:
- The number of nodes in the given list will be between 1 and 100.
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。
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。
