【LeetCode】 876. Middle of the Linked List 链表的中间结点（Easy）（JAVA）
题目地址: https://leetcode.com/problems/middle-of-the-linked-list/
题目描述：
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
给定一个带有头结点 head 的非空单链表，返回链表的中间结点。
如果有两个中间结点，则返回第二个中间结点。
解题方法
采用双指针，快指针两倍速度 2 * n，慢指针一倍速 n，快指针到结尾，慢指针刚好到中间
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode middleNode(ListNode head) {
ListNode fast = head;
while (fast != null && fast.next != null) {
fast = fast.next.next;
head = head.next;
}
return head;
}
}
执行用时 : 0 ms, 在所有 Java 提交中击败了 100.00% 的用户
内存消耗 : 36.5 MB, 在所有 Java 提交中击败了 5.05% 的用户
