백준 7576. 토마토 :: 돼지개발자

출저 : https://www.acmicpc.net/problem/7576

"단순 BFS"

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 N,M;
    static int[][] map;
    static int[] dx = {0,0,1,-1};
    static int[] dy = {1,-1,0,0};
    static Queue<Node> q = new LinkedList<>();
    static int day;
    
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        
        M = Integer.parseInt(st.nextToken());
        N = Integer.parseInt(st.nextToken());
        
        map = new int[N][M];
        
        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());
                map[i][j] = temp;
                
                if(temp == 1) {
                    q.add(new Node(i, j));
                }
            }
        }
        
        while(!q.isEmpty()) {
            
            int size = q.size();
            
            for (int s = 0; s < size; s++) {
                Node cur = q.poll();
                
                for (int i = 0; i < 4; i++) {
                    int nx = cur.x + dx[i];
                    int ny = cur.y + dy[i];
                    
                    if(!isRange(nx, ny) || map[nx][ny] != 0)
                        continue;
                    
                    map[nx][ny] = 1;
                    q.add(new Node(nx, ny));
                }
            }
            day++;
        }
        System.out.println(check() ? day-1: -1);
    }
    
    static boolean check() {
        for (int i = 0; i < N; i++) {
            for (int j = 0; j < M; j++) {
                if(map[i][j] == 0) return false;
            }
        }
        return true;
    }
    
    static boolean isRange(int x , int y) {
        if(x < 0 || x >= N || y < 0 || y >= M) return false;
        return true;
    }
}
 
class Node {
    int x;
    int y;
    
    Node( int x, int y ) {
        this.x = x;
        this.y = y;
    }
}