Kattis Fire Solution

Fire.java

package com.algorithms;

/**
 * @Author Mehdi Maick
 * Created on 22/09/2016.
 */

import java.awt.*;
import java.util.*;
import java.io.*;

public class Fire {
    static int[] dx = {1, -1, 0, 0};
    static int[] dy = {0, 0, 1, -1};
    static char[][] map;
    static int[][] dist, fdist;
    static int sx, sy;

    public static void solve(FastReader fs, PrintWriter pw) {
        int t = fs.nextInt();
        while (t-- > 0) {
            int m = fs.nextInt();
            int n = fs.nextInt();
            map = new char[n][m];
            dist = new int[n][m];
            for (int i = 0; i < n; i++) {
                Arrays.fill(dist[i], -1);
            }
            Queue<Cell> q = new ArrayDeque<>();
            for (int i = 0; i < n; i++) {
                map[i] = fs.nextLine().trim().toCharArray();
                for (int j = 0; j < map[i].length; j++) {
                    if (map[i][j] == '@') {
                        q.add(new Cell(i, j, '@'));
                        dist[i][j] = 0;
                    }
                }
            }
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    if (map[i][j] == '*') {
                        q.add(new Cell(i, j, '*'));
                    }
                }
            }
            int ans = -1;
            while (!q.isEmpty()) {
                Cell node = q.poll();
                if (node.type == '@' && map[node.x][node.y] == '*')
                    continue;
                if (node.type == '@' && (node.y == 0 || node.y == m - 1 || node.x == 0 || node.x == n - 1)) {
                    ans = dist[node.x][node.y] + 1;
                    break;
                }
                for (int i = 0; i < 4; i++) {
                    int x = node.x + dx[i];
                    int y = node.y + dy[i];
                    if (y < 0 || y >= m || x < 0 || x >= n)
                        continue;
                    if (map[x][y] == '#' || map[x][y] == '*')
                        continue;
                    if (node.type == '@' && dist[x][y] == -1) {
                        dist[x][y] = dist[node.x][node.y] + 1;
                        q.add(new Cell(x, y, '@'));
                    }
                    if (node.type == '*') {
                        q.add(new Cell(x, y, '*'));
                        map[x][y] = '*';
                    }
                }
            }
            if (ans == -1) {
                pw.println("IMPOSSIBLE");
            } else {
                pw.println(ans);
            }
        }
    }

    static class Cell {
        int x, y;
        char type;

        public Cell(int x, int y, char type) {
            this.x = x;
            this.y = y;
            this.type = type;
        }
    }

    public static void main(String[] args) throws Exception {
        FastReader fs = new FastReader(System.in);
        PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out));

        solve(fs, pw);

        fs.close();
        pw.close();
    }

    static class FastReader {

        BufferedReader reader;
        StringTokenizer st;

        FastReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream));
            st = null;
        }

        String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    String line = reader.readLine();
                    if (line == null) {
                        return null;
                    }
                    st = new StringTokenizer(line);
                } catch (Exception e) {
                    throw new RuntimeException();
                }
            }
            return st.nextToken();
        }

        String nextLine() {
            String s = null;
            try {
                s = reader.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return s;
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        char nextChar() {
            return next().charAt(0);
        }

        int[] nextIntArray(int n) {
            int[] arr = new int[n];
            int i = 0;
            while (i < n) {
                arr[i++] = nextInt();
            }
            return arr;
        }

        long[] nextLongArray(int n) {
            long[] arr = new long[n];
            int i = 0;
            while (i < n) {
                arr[i++] = nextLong();
            }
            return arr;
        }

        int[] nextIntArrayOneBased(int n) {
            int[] arr = new int[n + 1];
            int i = 1;
            while (i <= n) {
                arr[i++] = nextInt();
            }
            return arr;
        }

        long[] nextLongArrayOneBased(int n) {
            long[] arr = new long[n + 1];
            int i = 1;
            while (i <= n) {
                arr[i++] = nextLong();
            }
            return arr;
        }

        void close() {
            try {
                reader.close();
            } catch (IOException e) {
                System.err.println("There's been an error trying closing the reader ");
                e.printStackTrace();
            }
        }
    }


}