Middle of the Linked List

Given a non-empty, singly linked list with head nodehead, 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.

Solution

/**
* 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 slow = head;
ListNode fast = head;
while (fast != null && fast.next != null) {
slow = slow.next;
fast = fast.next.next;
}
return slow;
}
}