백준 - 2667

https://www.acmicpc.net/problem/2667

2667번: 단지번호붙이기

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

public class Main {
    static int[][] arr;
    static boolean[][] visited;
    static int N, count;
    static ArrayList<Integer> result;
    static int[] dx = {-1, 1, 0, 0};
    static int[] dy = {0, 0, -1, 1};

    public static void main(String[] args) throws NumberFormatException, IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        N = Integer.parseInt(br.readLine());
        arr = new int[N][N];
        visited = new boolean[N][N];
        result = new ArrayList<>();

        for (int i = 0; i < N; i++) {
            String str = br.readLine();
            for (int j = 0; j < N; j++) {
                arr[i][j] = str.charAt(j) - '0';
            }
        }

        for (int i = 0; i < N; i++) {
            for (int j = 0; j < N; j++) {
                if (arr[i][j]  == 1 && !visited[i][j]) {
                    count = 0;
                    dfs(i, j);
                    result.add(count);
                }
            }
        }

        Collections.sort(result);

        bw.write(String.valueOf(result.size()));
        bw.newLine();
        for (Integer integer : result) {
            bw.write(String.valueOf(integer));
            bw.newLine();
        }

        bw.flush();
    }

    public static void dfs(int y, int x) {
        visited[y][x] = true;
        count++;

        for (int i = 0; i < 4; i++) {
            int newX = x + dx[i];
            int newY = y + dy[i];

            if (newX < 0 || newX >= N || newY < 0 || newY >= N) continue;

            if (arr[newY][newX] == 1 && !visited[newY][newX])
                dfs(newY, newX);
        }
    }
}