[알고리즘] 백준 - 2667 ( 단지 번호 붙이기 ) / 자바 (DFS)

import java.util.*;
import java.io.*;
class Main {
	static int N ;
	static int count;
	static int dangCount = 0;
	static int map[][];
	static boolean check[][];
	
	static int dx[] = { 0 , 1 , 0 , -1 };
	static int dy[] = {1 , 0 , -1 , 0};
	static StringBuilder sb = new StringBuilder();
	
	public static void main(String args[]) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		N = Integer.parseInt(br.readLine());
		map = new int [N+2][N+2];
		check = new boolean[N+2][N+2];
		int answer[] = new int[N*N];
		for(int i = 1; i <= N ; i ++) {
			String s = br.readLine();
			for(int j = 0 ; j < N; j++) {
				map[i][j+1] = s.charAt(j)-'0';
			}
		}
		
		
		for (int i = 0; i < map.length; i++) {
			for(int j = 0 ; j < map.length; j++) {
				if(map[i][j] ==1 && !check[i][j] ) {
					count = 0;
					dfs(i,j);
					answer[dangCount] = count;
					dangCount ++;
				}
			}
		}
		sb.append(dangCount).append("\n");
		Arrays.sort(answer, 0, dangCount);

		for(int i = 0 ; i  < dangCount ; i ++) {
			sb.append(answer[i]).append("\n");
		}
		
		System.out.println(sb);
		
	}
	
	private static void dfs(int x, int y) {
		count += 1;
		check[x][y] = true;
		for(int i = 0 ; i < 4; i ++) {
			int nextX = x + dx[i];
			int nextY = y + dy[i];
			if(map[nextX][nextY] == 1 && !check[nextX][nextY]) {
				dfs(nextX , nextY);
			}
		}
	}
	
	
}