import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.LinkedList; import java.util.Queue; import java.util.StringTokenizer; public class Main { public static void main(String[] args) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st = new StringTokenizer(br.readLine()); int R = Integer.parseInt(st.nextToken()) + 1; // 행 int C = Integer.parseInt(st.nextToken()) + 1; // 열 int[][] board = new int[R][C]; int[][] jdp = new int[R][C]; int[][] fdp = new int[R][C]; Queue q = new LinkedList<>(); Queue fq = new LinkedList<>(); for (int i = 1; i < R; i++) { String s = br.readLine(); for (int j = 1; j < C; j++) { char c = s.charAt(j - 1); if (c == '.') { board[i][j] = 1; jdp[i][j] = -1; fdp[i][j] = -1; } else if (c == 'J') { q.offer(new Pair(i, j)); jdp[i][j] = 1; } else if (c == 'F') { fq.offer(new Pair(i, j)); } else if (c == '#') board[i][j] = -1; } } int[] dx = {-1, 0, 1, 0}; int[] dy = {0, -1, 0, 1}; while (!q.isEmpty()) { Pair cur = q.poll(); for (int dir = 0; dir < 4; dir++) { int nx = cur.x + dx[dir]; int ny = cur.y + dy[dir]; if (nx < 1 || ny < 1 || nx >= R || ny >= C) continue; if (jdp[nx][ny] >= 0 || board[nx][ny] != 1) continue; jdp[nx][ny] = jdp[cur.x][cur.y] + 1; q.add(new Pair(nx, ny)); } } while (!fq.isEmpty()) { Pair cur = fq.poll(); for (int dir = 0; dir < 4; dir++) { int nx = cur.x + dx[dir]; int ny = cur.y + dy[dir]; if (nx < 1 || ny < 1 || nx >= R || ny >= C) continue; if (fdp[nx][ny] >= 0 || board[nx][ny] == -1) continue; fdp[nx][ny] = fdp[cur.x][cur.y] + 1; fq.add(new Pair(nx, ny)); } } int min = Integer.MAX_VALUE; Pair pos = null; for (int i = 1; i < R; i++) { for (int j = 1; j < C; j++) { if (i == 1 || i == R - 1) { if (jdp[i][j] > 0 && jdp[i][j] < min) { min = jdp[i][j]; pos = new Pair(i, j); } } else { if (j == 1 || j == C - 1) { if (jdp[i][j] > 0 && jdp[i][j] < min) { min = jdp[i][j]; pos = new Pair(i, j); } } } } } if (pos == null) { System.out.println("IMPOSSIBLE"); return; } if (fdp[pos.x][pos.y] > 0 && fdp[pos.x][pos.y] <= min) System.out.println("IMPOSSIBLE"); else System.out.println(min); } private static class Pair { int x, y; public Pair(int x, int y) { this.x = x; this.y = y; } } }

제출 #30967

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