불 - 5427번

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내 코드

package com.company;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.StringTokenizer;

public class Main {
    static char[][] arr;
    static int w, h, time;
    static Queue<int[]> fireQ = new LinkedList<>();
    static PriorityQueue<Node> pq = new PriorityQueue<>();
    static int[][] way = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
    static boolean[][] visited;

    public static void main(String args[]) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = null;

        int T = Integer.parseInt(br.readLine());

        for (int tc = 0; tc < T; tc++) {
            boolean check = false;

            fireQ.clear();
            pq.clear();

            st = new StringTokenizer(br.readLine());
            w = Integer.parseInt(st.nextToken());
            h = Integer.parseInt(st.nextToken());
            time = 0;

            arr = new char[h + 2][w + 2];
            visited = new boolean[h + 2][w + 2];

            for (int i = 1; i <= h; i++) {
                String s = br.readLine();
                for (int j = 1; j <= w; j++) {
                    arr[i][j] = s.charAt(j - 1);
                    if (arr[i][j] == '*') {
                        fireQ.add(new int[]{i, j});
                    }
                    if (arr[i][j] == '@')
                        pq.add(new Node(i, j, 0));
                }
            }

            while (!pq.isEmpty()) {
                Node node = pq.poll();

                if (visited[node.x][node.y] || arr[node.x][node.y] == '*')
                    continue;

                visited[node.x][node.y] = true;

                if (node.x == 0 || node.y == 0 || node.x == h + 1 || node.y == w + 1) {
                    check = true;
                    time = node.dis;
                    break;
                }

                if (time == node.dis) {
                    fire(fireQ.size());
                    time++;
                }

                for (int i = 0; i < 4; i++) {
                    int x = node.x + way[i][0];
                    int y = node.y + way[i][1];

                    if (!visited[x][y] && arr[x][y] != '#' && arr[x][y] != '*') {
                        pq.add(new Node(x, y, node.dis + 1));
                        arr[x][y] = '@';
                    }
                }

            }

            if (check)
                System.out.println(time);
            else
                System.out.println("IMPOSSIBLE");

        }
    }

    static void fire(int size) {
        for (int i = 0; i < size; i++) {
            int[] index = fireQ.poll();

            for (int j = 0; j < 4; j++) {
                int x = index[0] + way[j][0];
                int y = index[1] + way[j][1];

                if (x >= 1 && x < h + 1 && y >= 1 && y < w + 1 && arr[x][y] != '#' && arr[x][y] != '*') {
                    arr[x][y] = '*';
                    fireQ.add(new int[]{x, y});
                }
            }
        }
    }
}

class Node implements Comparable<Node> {
    int x, y, dis;

    public Node(int x, int y, int dis) {
        this.x = x;
        this.y = y;
        this.dis = dis;
    }

    @Override
    public int compareTo(Node o) {
        return dis - o.dis;
    }
}