백준 - 7576번

 

 

풀이

 

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

public class Main {
	
	public static String[][] arr	= null;
	public static int[] changeX	= {-1, 1, 0, 0};
	public static int[] changeY	= {0, 0, -1, 1};
	public static int day		= -1;
    
	public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader br	= new BufferedReader(new InputStreamReader(System.in));
		String[] arrNum		= br.readLine().split(" ");
		arr			= new String[Integer.parseInt(arrNum[1])][Integer.parseInt(arrNum[0])];
		
		for(int i=0; i<arr.length; i++) {
			arr[i] = br.readLine().split(" ");
		}
		
		roop();

		System.out.println(day);
	}
	
	public static void roop() {
		Queue<Node> que = new LinkedList<>();

		for(int i=0; i<arr.length; i++) {
			for(int j=0; j<arr[0].length; j++) {
				if("1".equals(arr[i][j])) {
					que.add(new Node(i, j));
				}
			}
		}
		
		while(!que.isEmpty()) {
			int dayPlusFlay = que.size();
			
			day++;
			
			for(int i=0; i<dayPlusFlay; i++) {
				Node getNode = que.poll();
				
				arr[getNode.x][getNode.y] = "2";
				
				for(int j=0; j<4; j++) {
					int nextX = getNode.x + changeX[j];
					int nextY = getNode.y + changeY[j];
					
					if(nextX >= 0 && nextX < arr.length && nextY >= 0 && nextY < arr[0].length) {
						if("0".equals(arr[nextX][nextY])) {
							arr[nextX][nextY] = "1";
							que.add(new Node(nextX, nextY));
						}
					}
				}
			}			
		}
		
		for(int i=0; i<arr.length; i++) {
			for(int j=0; j<arr[0].length; j++) {
				if("0".equals(arr[i][j])) {
					day = -1;
					i = arr.length;
					j = arr[0].length;
				}
			}
		}
	}
	
	public static class Node {
		int x;
		int y;
		
		Node(int x, int y) {
			this.x = x;
			this.y = y;
		}
	}
}