876. Middle of the Linked List
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.
链表的中间位置
给定具有头节点头的非空的单链表，返回链表的中间节点。如果有两个中间节点，则返回第二个中间节点。
思路：定义两个链表，为 temp 与 rate。temp 每次走一步，rate 每次走两步，当 rate 走完的时候，temp 刚好到中间位置。需要注意的是链表总数为偶数的情况下，需要返回 temp.next。
public ListNode middleNode(ListNode head) {
ListNode temp = head;
ListNode rate = head;
while (rate != null && rate.next != null){
if (rate.next != null && rate.next.next == null){
return temp.next;
}
temp = temp.next;
rate = rate.next.next;
}
return temp;
}
