문제는 다음과 같습니다.

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

　
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class Test{
	static int N;
	static int[][] adMatrix;
	static int[][] visit;
	static int dx[] = {0, -1, 0, 1};
	static int dy[] = {-1, 0, 1, 0};
	static ArrayList<Integer> list = new ArrayList<Integer>();
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		N = sc.nextInt();
		adMatrix = new int[N+1][N+1];
		visit = new int[N+1][N+1];
		String[] s = new String[N+1];
		for(int i=1; i<=N; i++) {
			s[i] = sc.next();
			for(int j=1; j<=N; j++) {
				adMatrix[i][j] = s[i].charAt(j-1)-'0';
			}
		}
		
		int totalCNT=0;
		for(int i=1; i<=N; i++) {
			for(int j=1; j<=N; j++) {
				if(adMatrix[i][j]==1 && visit[i][j]==0) {
					totalCNT++;
					int cnt = DFS(i,j, totalCNT, 0);
					list.add(cnt);
				}
			}
		}
		Collections.sort(list); //오름차순 정렬함수
		System.out.println(totalCNT);
		for(int x : list) {
			System.out.println(x);
		}
	}
	static int DFS(int row, int col, int totalCNT, int cnt) {
		cnt++;
		visit[row][col] = 1; //1 true, 0 false
		for(int i=0; i<4; i++) {
			int nextRow = row + dx[i];
			int nextCol = col + dy[i];
			if(nextRow>0 && nextRow<=N && nextCol>0 && nextCol<=N) {
				if(adMatrix[nextRow][nextCol]==1 && visit[nextRow][nextCol]==0) {
					cnt = DFS(nextRow, nextCol, totalCNT, cnt);
				}
			}
		}
		return cnt;
	}
	
	
}
　

결과입니다.