백준 2667

package baekjoon.DFS와BFS;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

//단지 번호 붙이기
// https://www.acmicpc.net/problem/2667
public class Main2667 {

   private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
   private static int N, cnt;
   private static List<Integer> ans = new ArrayList<>();
   private static int[] dy = {-1, 0, 1, 0};
   private static int[] dx = {0, 1, 0, -1};
   private static int[][] map;
   private static boolean[][] visited;
   private static StringBuilder sb = new StringBuilder();

   public static void main(String[] args) throws Exception {
      input();
      go();
      print();
   }

   private static void print() {
      Collections.sort(ans);
      sb.append(ans.size()).append('\n');
      for (Integer a : ans) {
         sb.append(a).append('\n');
      }
      System.out.println(sb);
   }

   private static void go() {
      for (int i = 0; i < N; i++) {
         for (int j = 0; j < N; j++) {
            if (map[i][j] == 0 || visited[i][j])
               continue;
            cnt = 0;
            DFS(i, j);
            ans.add(cnt);
         }
      }
   }

   private static void input() throws IOException {
      N = Integer.parseInt(br.readLine());
      map = new int[N][N];
      visited = new boolean[N][N];
      for (int i = 0; i < N; i++) {
         String s = br.readLine();
         for (int j = 0; j < s.length(); j++) {
            map[i][j] = s.charAt(j) - '0';
         }
      }
   }

   private static int DFS(int y, int x) {
      visited[y][x] = true;
      cnt++;
      for (int i = 0; i < 4; i++) {
         int ny = y + dy[i];
         int nx = x + dx[i];
         if (isMap(ny, nx) || visited[ny][nx] || map[ny][nx] == 0)
            continue;
         visited[ny][nx] = true;
         DFS(ny, nx);
      }
      return cnt;
   }

   private static boolean isMap(int ny, int nx) {
      return ny >= N || nx >= N || ny < 0 || nx < 0;
   }
}