Middle of the Linked List
<p>Given the <code>head</code> of a singly linked list, return <em>the middle node of the linked list</em>.</p>

<p>If there are two middle nodes, return <strong>the second middle</strong> node.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0800-0899/0876.Middle%20of%20the%20Linked%20List/images/lc-midlist1.jpg" style="width: 544px; height: 65px;" />
<pre>
<strong>Input:</strong> head = [1,2,3,4,5]
<strong>Output:</strong> [3,4,5]
<strong>Explanation:</strong> The middle node of the list is node 3.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0800-0899/0876.Middle%20of%20the%20Linked%20List/images/lc-midlist2.jpg" style="width: 664px; height: 65px;" />
<pre>
<strong>Input:</strong> head = [1,2,3,4,5,6]
<strong>Output:</strong> [4,5,6]
<strong>Explanation:</strong> Since the list has two middle nodes with values 3 and 4, we return the second one.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the list is in the range <code>[1, 100]</code>.</li>
	<li><code>1 &lt;= Node.val &lt;= 100</code></li>
</ul>
Linked List; Two Pointers
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode middleNode(ListNode head) {
        ListNode slow = head, fast = head;
        while (fast != null && fast.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }
        return slow;
    }
}