输出单向链表中倒数第k个结点

实现代码：

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        while (scanner.hasNextInt()) {
            int n = scanner.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = scanner.nextInt();
            }
            int k = scanner.nextInt();

            // 构建链表
            ListNode head = new ListNode(arr[0]);
            ListNode current = head;
            for (int i = 1; i < n; i++) {
                current.next = new ListNode(arr[i]);
                current = current.next;
            }

            // 寻找倒数第k个节点
            ListNode result = findKthFromEnd(head, k);
            System.out.println(result.val);
        }

        scanner.close();
    }

    public static ListNode findKthFromEnd(ListNode head, int k) {
        ListNode fast = head;
        ListNode slow = head;

        // 快指针先走k步
        for (int i = 0; i < k; i++) {
            fast = fast.next;
        }

        // 快慢指针一起走，直到快指针到达末尾
        while (fast != null) {
            fast = fast.next;
            slow = slow.next;
        }

        return slow;
    }
}

class ListNode {
    int val;
    ListNode next;
    ListNode(int x) {
        val = x;
        next = null;
    }
}