백준 21922: 학부 연구생 민상(java)

https://www.acmicpc.net/problem/21922

package Baekjoon.boj21922;

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

public class Main {
    static int[][] map = new int[2001][2001];
    static int N, M, cnt;
    static boolean[][][] visit;
    // 인덱스에 따른 방향 : 0 : ↑, 1 : →, 2 : ↓, 3 : ←
    static int[] dx = {0, 1, 0, -1};
    static int[] dy = {-1, 0, 1, 0};
    static class Node {
        int y, x, dir;
        public Node(int y, int x, int dir) {
            this.y = y;
            this.x = x;
            this.dir = dir;
        }
    }

    static Queue<Node> q = new LinkedList<Node>();

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken());
        visit = new boolean[N][M][4];

        for (int i = 0; i < N; i++) {
            st = new StringTokenizer(br.readLine());
            for (int j = 0; j < M; j++) {
                int temp = Integer.parseInt(st.nextToken());
                if(temp == 9) {
                    for (int dir = 0; dir < 4; dir++) {
                        visit[i][j][dir] = true;
                        q.add(new Node(i, j, dir));
                    }
                }
                map[i][j] = temp;
            }
        }

        bfs();

        for (int i = 0; i < N; i++) {
            for (int j = 0; j < M; j++) {
                for (int dir = 0; dir < 4; dir++) {
                    if(visit[i][j][dir]) {
                        cnt++;
                        break;
                    }
                }
            }
        }

        System.out.println(cnt);
    }

    public static void bfs() {
        while(!q.isEmpty()) {
            Node cur = q.poll();

            int nx = cur.x + dx[cur.dir];
            int ny = cur.y + dy[cur.dir];

            if(nx < 0 || nx >= M || ny < 0 || ny >= N) continue;
            if(visit[ny][nx][cur.dir]) continue;

            visit[ny][nx][cur.dir] = true;

            switch(map[ny][nx]) {
                case 1 :
                    if(cur.dir == 1 || cur.dir == 3) continue;
                    break;
                case 2 :
                    if(cur.dir == 0 || cur.dir == 2) continue;
                    break;
                case 3 :
                    if(cur.dir == 0) cur.dir = 1;
                    else if(cur.dir == 1) cur.dir = 0;
                    else if(cur.dir == 2) cur.dir = 3;
                    else if(cur.dir == 3) cur.dir = 2;
                    break;
                case 4 :
                    if(cur.dir == 0) cur.dir = 3;
                    else if(cur.dir == 1) cur.dir = 2;
                    else if(cur.dir == 2) cur.dir = 1;
                    else if(cur.dir == 3) cur.dir = 0;
                    break;
            }

            q.add(new Node(ny, nx, cur.dir));
        }
    }

}