[소프티어 2Level] 장애물 인식 프로그램(Java)

import java.util.*;
import java.io.*;


public class Main
{
    static int[][] graph;
    static int[] dx = {0,1,0,-1};
    static int[] dy = {-1,0,1,0};
    static int n; 
    public static void main(String args[]) throws IOException
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    
        n = Integer.parseInt(br.readLine());
        graph = new int[n][n];
        
        for(int i = 0; i < n; i++){
            String[] str = br.readLine().split("");
            for(int j = 0; j < n ;j++){
                graph[i][j] = Integer.parseInt(str[j]);
            }
        }
        ArrayList<Integer> result = new ArrayList<>();
        for(int i = 0; i < n; i++){
            for(int j = 0; j < n; j++){
                if(graph[i][j] == 1){
                    result.add(BFS(i,j));
                }
            }
        }
        Collections.sort(result);
        System.out.println(result.size());
        for(int a : result)
            System.out.println(a);
        //System.out.print(Arrays.deepToString(graph));

    }
    static int BFS(int y, int x){
        Queue<int[]> queue = new LinkedList<>();
        graph[y][x] = 0;
        int count = 1;
        queue.add(new int[]{y,x});
        while(queue.size() > 0){
            int[] current = queue.poll();

            for(int i = 0; i < 4; i++){
                int nextY = current[0] + dy[i];
                int nextX = current[1] + dx[i];
                if(0 <= nextY && nextY < n && 0 <= nextX && nextX < n)
                {
                    if(graph[nextY][nextX] == 1){
                        graph[nextY][nextX] = 0;
                        count++;
                        queue.add(new int[]{nextY, nextX});
                    }
                }

            }
        }
        return count;
    }
}