kingsubin

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

public class boj_4179 {
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    static StringTokenizer st;
    static Queue<Node> qF = new LinkedList<>();
    static Queue<Node> qJ = new LinkedList<>();
    static char[][] a;
    static int row, col, nx, ny, ans;
    static int[] dx = {-1, 1, 0, 0};
    static int[] dy = {0, 0, -1, 1};

    public static void main(String[] args) throws IOException {
        input();
        if (bfs()) System.out.println(ans);
        else System.out.println("IMPOSSIBLE");
    }

    public static void input() throws IOException {
        st = new StringTokenizer(br.readLine());

        row = Integer.parseInt(st.nextToken());
        col = Integer.parseInt(st.nextToken());
        a = new char[row][col];

        for (int i = 0; i < row; i++) {
            a[i] = br.readLine().toCharArray();
            for (int j = 0; j < col; j++) {
                if (a[i][j] == 'F') {
                    qF.offer(new Node(i, j, 0));
                } else if (a[i][j] == 'J') {
                    qJ.offer(new Node(i, j, 0));
                }
            }
        }
    }

    public static boolean bfs() {
        while (!qJ.isEmpty()) {

            int size = qF.size();
            for (int i = 0; i < size; i++) {
                Node now = qF.poll();

                for (int j = 0; j < 4; j++) {
                    nx = now.x + dx[j];
                    ny = now.y + dy[j];

                    if (nx < 0 || nx >= row || ny < 0 || ny >= col) continue;
                    if (a[nx][ny] == '#' || a[nx][ny] == 'F') continue;

                    a[nx][ny] = 'F';
                    qF.offer(new Node(nx, ny, now.d + 1));
                }
            }

            size = qJ.size();
            for (int i = 0; i < size; i++) {
                Node now = qJ.poll();

                for (int j = 0; j < 4; j++) {
                    nx = now.x + dx[j];
                    ny = now.y + dy[j];

                    if (nx <  0 || nx >= row || ny < 0 || ny >= col) {
                        ans = now.d + 1;
                        return true;
                    }

                    if (a[nx][ny] == '#' || a[nx][ny] == 'F' || a[nx][ny] == 'J') continue;
                    a[nx][ny] = 'J';
                    qJ.offer(new Node(nx, ny, now.d + 1));
                }
            }
        }

        return false;
    }

    static private class Node {
        int x;
        int y;
        int d;

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

 

- 실패

 

- 불 먼저 이동후 - > 지훈이는 불을 피해다니며 이동

- 지훈이가 완전히 탈출할때까지 반복

- 지훈이가 만약 범위를 벗어난다면 그때의 시간인 now.d + 1을 출력후 return true

- 큐가 빌때까지 반복했는데도 탈출하지 못한다면 return false

- true : ans+1, false : impossible 출력