package LinkedLists;

/**
 * @author zhengstars
 * @date 2023/06/11
 */
public class MiddleoftheLinkedList {
    public static class ListNode {
        int val;
        ListNode next;

        ListNode(int val) {
            this.val = val;
            this.next = null;
        }
    }

    public static ListNode middleNode(ListNode head) {
        ListNode slow = head;
        ListNode fast = head;

        // Move the fast pointer two steps ahead and the slow pointer one step ahead
        // When the fast pointer reaches the end of the linked list, the slow pointer will be at the middle node
        while (fast != null && fast.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }

        // Return the middle node
        return slow;
    }

    public static void main(String[] args) {
        ListNode node1 = new ListNode(1);
        ListNode node2 = new ListNode(2);
        ListNode node3 = new ListNode(3);
        ListNode node4 = new ListNode(4);
        ListNode node5 = new ListNode(5);
        ListNode node6 = new ListNode(6);

        node1.next = node2;
        node2.next = node3;
        node3.next = node4;
        node4.next = node5;
        node5.next = node6;

        ListNode result = middleNode(node1);

        while (result != null) {
            System.out.print(result.val + " -> ");
            result = result.next;
        }
        System.out.println("null");
    }
}