[BOJ] 백준 17141-연구소2(java)

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;
 
public class Main{
    private static int N;
    private static int M;
    private static int[][] map;
    private static ArrayList<Pos> virusPos;
    private static int result;
    private static int[] dx = { 0, 1, 0, -1 };
    private static int[] dy = { 1, 0, -1, 0 };
    private static boolean check;
    private static Pos[] set;
 
 
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine(), " ");
        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken()); // 바이러스 놓을 수 있는 수
        map = new int[N][N];
        virusPos = new ArrayList<Pos>();
        set = new Pos[M];
        for (int i = 0; i < N; i++) {
            st = new StringTokenizer(br.readLine(), " ");
            for (int j = 0; j < N; j++) {
                map[i][j] = Integer.parseInt(st.nextToken());
                if (map[i][j] == 2) {
                    map[i][j] = 0;
                    virusPos.add(new Pos(i, j));
                }
                if(map[i][j] == 1) map[i][j] = -1;
            }
        }
        result = Integer.MAX_VALUE;
        check = false;
        combination(0, 0);
        if(result == Integer.MAX_VALUE) System.out.println("-1");
        else System.out.println(result);
 
    }// end of main
 
    
 
    public static void combination(int k, int len) {
        if (len == M) {
            process();
            return;
        } else {
            for (int i = k; i < virusPos.size(); i++) {
                set[len] = new Pos(virusPos.get(i).x, virusPos.get(i).y);
                combination(i + 1, len + 1);
            }
        }
    }
 
    public static void process() {
        Queue<Pos> queue = new LinkedList<Pos>();
        int[][] temp = new int[N][N];
        boolean[][] visited = new boolean[N][N];
        for (int i = 0; i < temp.length; i++) {
            System.arraycopy(map[i], 0, temp[i], 0, N);
        }
 
        for (int i = 0; i < set.length; i++) {
            temp[set[i].x][set[i].y] = -2;
            visited[set[i].x][set[i].y] = true;
            queue.add(new Pos(set[i].x, set[i].y));
        }
//        print(temp);
        int value = 1;
        while (!queue.isEmpty()) {
            int size = queue.size();
 
            for (int i = 0; i < size; i++) {
                Pos p = queue.poll();
                for (int j = 0; j < dx.length; j++) {
                    int nx = p.x + dx[j];
                    int ny = p.y + dy[j];
                    
                    if(nx >=0 && ny >=0 && nx < N && ny < N && map[nx][ny] !=-1 && !visited[nx][ny]) {
                        visited[nx][ny] = true;
                        temp[nx][ny] = value;
                        queue.add(new Pos(nx, ny));
                    }
                }
            }
            value++;
            
        }
//        print(temp);
        int time = 0;
        label :for (int j = 0; j < temp.length; j++) {
            for (int i = 0; i < temp.length; i++) {
                if(temp[i][j] == 0) {
                    check = false;
                    break label;
                }else {
                    if(time  < temp[i][j]) time = temp[i][j];
                    check = true;
                }
                
            }
        }
        if(check) {
            result = result > time ? time :result;
        }
        else return;
        
    }
 
    private static void print(int[][] temp) {
        // TODO Auto-generated method stub
        for (int i = 0; i < temp.length; i++) {
            for (int j = 0; j < temp.length; j++) {
                System.out.print(temp[i][j]);
            }
            System.out.println();
        }
        
        System.out.println("========================");
    }
 
    static class Pos {
        int x;
        int y;
 
        public Pos(int x, int y) {
            super();
            this.x = x;
            this.y = y;
        }
 
        @Override
        public String toString() {
            return "Pos [x=" + x + ", y=" + y + "]";
        }
 
    }
}// end of class