백준 7576 토마토

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.*;

public class Main {
	public static int nx []= {1,-1,0,0};
	public static int ny []= {0,0,-1,1};
	 
	public static void main(String[] args) {
	
		 Scanner sc=new Scanner(System.in);
		 int m=sc.nextInt();
		 int n=sc.nextInt();
		 
		 int arr [][]=new int [m+2][n+2];
		 int arr2 [][]=new int [m+2][n+2];
		 boolean check [][]=new boolean[m+2][n+2];
		 for(int i=0;i<m+2;i++) {
			 Arrays.fill(arr[i],-1);
			 Arrays.fill(arr2[i],-1);
			 Arrays.fill(check[i], false);
		 }
		  
		 for(int i=1;i<m+1;i++) {
			 for(int j=1;j<n+1;j++) {
				 arr[i][j]=sc.nextInt();
				 arr2[i][j]=arr[i][j];
			 }
		 }
		 
		 //--- 여기까지 세팅 끝 ---
		 int day=0;
		  
		 int flag=1;	
		 while(flag==1) {
			 flag=0;	 
			 
			 for(int i=1;i<m+1;i++) {
				 for(int j=1;j<n+1;j++) {
					  if(arr2[i][j]==1&&check[i][j]==false) {
						 
						  check[i][j]=true;
						  flag=1;
						 
						  for(int k=0;k<4;k++) {
							  //위아래옆이 0이면 
							  if(arr2[i+nx[k]][j+ny[k]]==0) {
								  arr[i+nx[k]][j+ny[k]]=1;
								  check[i+nx[k]][j+ny[k]]=false;								 
								 
							  }
									  
						  }			 
						  
					  }
					   		   
				 }
			 }  
			 
			 if(flag==1) {
					day++;
					for(int i=0;i<m+2;i++) {
						for(int j=0;j<n+2;j++) {
							arr2[i][j]= arr[i][j];
						}
					} 
				}
			  
	 
		 }
		 
		 boolean ans=true;
			for(int i=0;i<m+2;i++) {
				for(int j=0;j<n+2;j++) {
					if(arr2[i][j]==0) ans=false;
				}
			} 
			 if(ans==true) System.out.println(day); 
			 else System.out.println(-1);
		 
		  
		 
	
	
	}
}

처음엔 배열 두개로 풀었는데  

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.*;

public class Main {
	public static int nx []= {1,-1,0,0};
	public static int ny []= {0,0,-1,1};
	 
	public static void main(String[] args) {
	
		 Scanner sc=new Scanner(System.in);
		 int m=sc.nextInt();
		 int n=sc.nextInt();
		 int[][] arr = new int[m][n];
	     int cnt = 0;
	     int day = 0;
	     Queue<int[]> q = new LinkedList<>();
	     
	     for(int j=0;j<n;j++) {
	    	 for(int i=0;i<m;i++) {
	    		 arr[i][j]=sc.nextInt();
	    		 if(arr[i][j]==1) {
	    			 q.add(new int [] {i,j});
	    		 }
	    		 else if(arr[i][j]==0)
	    			 cnt++;
	    		 
	    	 }
	     }
	   
	     
	     //---세팅 끝---
	     //cnt는 토마토 갯수만큼 있음. 토마토 익힐 때마다 cnt--하고, cnt가 0이되면 탈출
	     while(!q.isEmpty()&&cnt>0) {
	    	 for (int s = q.size(); s > 0; s--) {
	    		 int temp []=q.poll();
		    	 for(int k=0;k<4;k++) {
		    		 int x=temp[0]+nx[k];
		    		 int y=temp[1]+ny[k];
		    		 //인덱스 범위 넘지 않도록
		    		 
		    		 if(x>=0&&y>=00&&x<m&&y<n) {
		    			 if(arr[x][y]==0) {
			    			 arr[x][y]=1;
			    			 cnt--;
			    			 q.add(new int [] {x,y});
			    		 }
		    			 else {
		    				 continue;
		    			 }
		    		 } 
		    	 
		    		 
		    	 } 
	    	 }
	    	  
	    	 day++;
	     }
	      
	     //답 출력 
	     if(cnt==0)
	    	 System.out.println(day);
	     else
	    	 System.out.println(-1);
	     
	    
	}
}

큐를 이용한 bfs 풀이가 맞는것같아서 다시풀었다