阿里 LeetCode 876.链表的中间节点

附代码：

class Solution {
    public ListNode middleNode(ListNode head) {
        ListNode fast = head,slow = head;
        while(fast != null && fast.next != null){
            fast = fast.next.next;
            slow = slow.next;
        }
        return slow;
    }
}

ACM模式：

import java.util.Scanner;

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

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] nums = new int[n];
        for(int i = 0;i < n;i++){
            nums[i] = scanner.nextInt();
        }
        ListNode head = null;
        if(n > 0){
            head = new ListNode(nums[0]);
            ListNode cur = head;
            for(int i = 1;i < n;i++){
                cur.next = new ListNode(nums[i]);
                cur = cur.next;
            }
        }
        Solution solution = new Solution();
        ListNode mid = solution.middleNode(head);
        System.out.println(mid.val);
        scanner.close();
    }
}
class Solution {
    public ListNode middleNode(ListNode head) {
        ListNode fast = head, slow = head;
        while (fast != null && fast.next != null) {
            fast = fast.next.next;
            slow = slow.next;
        }
        return slow;
    }
}