[Softeer] 동계 테스트 시점 예측 (lv.3)

https://softeer.ai/practice/info.do?eventIdx=1&psProblemId=411&sw_prbl_sbms_sn=27754 

Softeer

2021

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import java.util.*;
import java.io.*;
 
 
public class Main {
    public static int N, M, answer;
    public static int[][] arr;
    public static int[] dx = {-1, 0, 1, 0};
    public static int[] dy = {0, -1, 0, 1};
 
    public static void init() {
        Queue<int[]> q = new LinkedList<>();
        q.add(new int[]{0, 0});
        boolean[][] vtd = new boolean[N][M];
        vtd[0][0] = true;
        arr[0][0] = -1;
 
        while(!q.isEmpty()) {
            int[] tmp = q.poll();
            int x = tmp[0];
            int y = tmp[1];
 
            for(int i = 0; i < 4; i++) {
                int nx = x + dx[i];
                int ny = y + dy[i];
 
                if(nx < 0 || ny < 0 || nx >= N || ny >= M || vtd[nx][ny] || arr[nx][ny] == 1) continue;
                else {
                    arr[nx][ny] = -1;
                    vtd[nx][ny] = true;
                    q.add(new int[]{nx, ny});
                }
            }
        }
    }
 
    public static boolean check() {
        for(int i = 0; i < N; i++) {
            for(int j = 0; j < M; j++) {
                if(arr[i][j] == 1) return false;
            }
        }
        return true;
    }
 
    public static void solve(int x, int y) {
        int count = 0;
        for(int i = 0; i < 4; i++) {
            int nx = x + dx[i];
            int ny = y + dy[i];
            if(nx < 0 || ny < 0 || nx >= N || ny >= M || arr[nx][ny] != -1) continue;
            else if(arr[nx][ny] == -1) {
                count++;
            }
        }
        if(count >= 2) arr[x][y] = 2;
    }
 
    public static void melting() {
        for(int i = 0; i < N; i++)
            for(int j = 0; j < M; j++)
                if(arr[i][j] == 2) arr[i][j] = -1;
    }
 
    public static void main(String[] args) throws IOException {
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(bf.readLine());
        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken());
 
        arr = new int[N][M];
        answer = 0;
 
        for(int i = 0; i < N; i++) {
            st = new StringTokenizer(bf.readLine());
            for(int j = 0; j < M; j++) {
                arr[i][j] = Integer.parseInt(st.nextToken());
            }
        }
 
        while(true) {
            init();
            if(check()) break;
 
            for(int i = 0; i < N; i++) {
                for(int j = 0; j < M; j++) {
                    if(arr[i][j] == 1) {
                        solve(i, j);
                    }
                }
            }
            melting();
            answer++;
        }
 
        System.out.println(answer);
    }
}