9
3 4 2 5 3 8 4 6 9

4

import java.util.Scanner;
//1:无需package
//2: 类名必须Main, 不可修改
public class 小朋友崇拜圈 {
 public static void main(String[] args) {
     Scanner sc = new Scanner(System.in);
     int n = sc.nextInt();
     int[] a = new int[n + 1];
     for (int i = 1; i <= n; i++) {
         a[i] = sc.nextInt();
     }
     int maxl = 0;// 定义一个圈的最大长度
     for (int i = 1; i <= n; i++) {
         int len = dfs(a, i, 0);
         if (len > maxl) {
             maxl = len;
         }
     }
     System.out.println(maxl);
 }
 public static int dfs(int[] a, int i, int length) {
     int k = a[i];// 给定的第一个圈值开始找
     if (a[i] == k)// 和自己围圈就算1个长度
         length++;
     while (k != i) {
         k = a[k];// 寻找下一个圈
         length++;
         if (length > a.length)// 说明不能围成圈,直接运行终止
             return 0;
     }
     return length;
 }
}

3 6
2
2 2
3 4
1

9

import java.util.LinkedList;
import java.util.Scanner;
public class 灌溉 {
    static int dx[] ={0,1,0,-1};
    static int dy[] = {1,0,-1,0};
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        int v[][] = new int[n+1][m+1];
        int t = sc.nextInt();
        LinkedList<node> list = new LinkedList<>();
        for (int i = 0; i < t; i++) {
            int a = sc.nextInt();
            int b = sc.nextInt();
            v[a][b] = 1;
            list.add(new node(a,b,0));
        }
        int k = sc.nextInt();
        while (!list.isEmpty()){
            node p = list.poll();
            if (p.step==k)
                continue;
            for (int j = 0; j < 4; j++) {
                int tx = p.x+dx[j];
                int ty = p.y+dy[j];
                if (tx>0&&tx<=n&&ty>0&&ty<=m&&v[tx][ty]==0){
                    v[tx][ty] = 1;
                    list.add(new node(tx,ty,p.step+1));
                }
            }
        }
        int ans = 0;
        for (int i = 0; i < n+1; i++) {
            for (int j = 0; j < 1+m; j++) {
                if (v[i][j]==1){
                    ans++;
                }
            }
        }
        System.out.println(ans);
    }
}
class node{
    int x;
    int y;
    int step;
    public node(int x, int y, int step) {
        this.x = x;
        this.y = y;
        this.step = step;
    }
}