876.MiddleNode.cs

// 876. Middle of the Linked List
// Given the head of a singly linked list, return the middle node of the linked list.
// If there are two middle nodes, return the second middle node.
// Example 1:
// Input: head = [1,2,3,4,5]
// Output: [3,4,5]
// Explanation: The middle node of the list is node 3.
// Example 2:
// Input: head = [1,2,3,4,5,6]
// Output: [4,5,6]
// Explanation: Since the list has two middle nodes with values 3 and 4, we return the second one.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     public int val;
 *     public ListNode next;
 *     public ListNode(int val=0, ListNode next=null) {
 *         this.val = val;
 *         this.next = next;
 *     }
 * }
 */
public class Solution {
    public ListNode MiddleNode(ListNode head) {
        ListNode slow,fast;
        slow = fast = head;
        while(fast != null && fast.next != null){
            slow = slow.next;
            fast = fast.next.next;
        }
        return slow;
    }
}