[JAVA/백준] DFS와 BFS: 단지번호붙이기

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

/**
 * @author HEESOO
 *
 */
public class Main {
	static int n;
	static int cnt;
	static int[][] map;
	static boolean[][] visit;
	public static void dfs(int x, int y) {
		if(visit[x][y]) return;
		
		int[] dotX= {0,1,0,-1};
		int[] dotY= {-1,0,1,0};
		visit[x][y]=true;
		cnt++;
		for(int i=0;i<4;i++) {
			int xx=x+dotX[i];
			int yy=y+dotY[i];
			if(0<=xx&&xx<n&&0<=yy&&yy<n)
				if(map[xx][yy]==1&&!visit[xx][yy])
					dfs(xx, yy);
		}
		
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner scan = new Scanner(System.in);
		n=scan.nextInt();
		map=new int[n][n];
		visit=new boolean[n][n];
		for(int i=0;i<n;i++) {
			String str=scan.next();
			for(int j=0;j<n;j++) {
				map[i][j]=str.charAt(j)-'0';
			}
		}
		
		ArrayList<Integer> list=new ArrayList<>();
		for(int i=0;i<n;i++) {
			for(int j=0;j<n;j++) {
				if(map[i][j]==1&&!visit[i][j]) {
					cnt=0;
					dfs(i, j);
					list.add(cnt);
				}
			}
		}
		
		Collections.sort(list);
		System.out.println(list.size());
		for(int i=0;i<list.size();i++)
			System.out.println(list.get(i));
	}
}