[BOJ] 27211 도넛 행성 (JAVA)

https://www.acmicpc.net/problem/27211

27211번: 도넛 행성

 

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;

public class Main {
	
    public static void main(String[] args) throws Exception {

        int[] dr = { -1,  0,  1,  0 };
        int[] dc = {  0,  1,  0, -1 };
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine(), " ");
        int N = Integer.parseInt(st.nextToken());
        int M = Integer.parseInt(st.nextToken());
        int[][] map = new int[N][M];
        for (int i = 0; i < N; i++) {
            st = new StringTokenizer(br.readLine(), " ");
            for (int j = 0; j < M; j++) {
                map[i][j] = Integer.parseInt(st.nextToken());
            }
        } // end of input

        boolean[][] visited = new boolean[N][M];
        Queue<Pos> q = new LinkedList<>();
        int cnt = 0;

        for (int i = 0; i < N; i++) {

            for (int j = 0; j < M; j++) {

                if(map[i][j] == 0 && !visited[i][j]) {

                    q.offer(new Pos(i, j));
                    visited[i][j] = true;
                    cnt++;

                    while(!q.isEmpty()) {

                        Pos p = q.poll();

                        for (int dir = 0; dir < 4; dir++) {

                            int nr = p.row + dr[dir];
                            int nc = p.col + dc[dir];

                            if(nr < 0) nr = N - 1;
                            else if(N <= nr) nr = 0;
                            if(nc < 0) nc = M - 1;
                            else if(M <= nc) nc = 0;

                            if(map[nr][nc] == 0 && !visited[nr][nc]) {

                                visited[nr][nc] = true;
                                q.offer(new Pos(nr, nc));

                            }

                        }

                    }

                }

            }

        }

        System.out.println(cnt);

    }

    static class Pos {

        int row, col;

        public Pos(int row, int col) {
            this.row = row;
            this.col = col;
        }

    }

}