_876.java

package com.fishercoder.solutions;

import com.fishercoder.common.classes.ListNode;

/**
 * 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.
 *
 * Note:
 *
 * The number of nodes in the given list will be between 1 and 100.
 */
public class _876 {
  public static class Solution1 {
    public ListNode middleNode(ListNode head) {
      ListNode fast = head;
      ListNode slow = head;
      while (fast != null && fast.next != null) {
        fast = fast.next.next;
        slow = slow.next;
      }
      return slow;
    }
  }
}