백준 - 7576 토마토(feat. java)

import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

public class Main {
	
	static Queue<Point> q = new LinkedList<Point>();
	static int[][] map;
	static boolean[][] visited;
	static int[] dx = {-1,1,0,0};
	static int[] dy = {0,0,-1,1};
	static int N;
	static int M;
	
	public static class Point {
		int x;
		int y;
		
		Point(int x, int y) {
			this.x = x;
			this.y = y;
		}
	}
	
	public static void bfs(Queue<Point> q) {
		
		while(!q.isEmpty()) {
			
			Point p = q.poll();
			
			for (int i =0; i < 4; i++) {
				int nextX = p.x + dx[i];
				int nextY = p.y + dy[i];
				
				if (nextX < 0 || nextY <0 || nextX >= M || nextY >=N) continue;
				if (map[nextX][nextY] != 0) continue;
				
				q.add(new Point(nextX,nextY));
				
				map[nextX][nextY] = map[p.x][p.y]+1;
				
			}
		}
		
		int max = 0; 
		
		for (int i = 0; i < N; i++) {
			for (int j = 0; j < M; j++) {
				if (map[j][i] == 0) {
					System.out.println(-1);
					return;
				}
				max = Math.max(max, map[j][i]);
				
			}
		}
		
		System.out.println(max-1);
	}
	
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in); 
		
		M = sc.nextInt();
		N = sc.nextInt();
		
		map = new int[M][N];
		visited = new boolean[M][N];
		
		for (int i = 0; i < N; i++) {
			
			for (int j = 0; j < M; j++) {
				map[j][i] = sc.nextInt();
				
				if (map[j][i] == 1) {q.add(new Point(j,i));}
				
			}
		}
		
		
		bfs(q);

		
	}
}