[20250306] BOJ / G3 / 불! / 신동윤

03do-new30/202503/06 BOJ G3 불!.md

@@ -0,0 +1,100 @@
+```java
+import java.util.*;
+import java.io.*;
+public class Main {
+
+	static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+	static int R, C;
+	static char[][] arr;
+	static int[][] fireTime;
+	static int[] dr = {0, 0, -1, 1};
+	static int[] dc = {-1, 1, 0, 0};
+
+	public static void main(String[] args) throws IOException{
+
+		input();
+		setFireTime();
+		int result = bfs();
+		System.out.println(result == -1 ? "IMPOSSIBLE" : result);
+
+	}
+
+	static int bfs() {
+		int[][] time = new int[R][C];
+		Queue<int[]> q = new ArrayDeque<>();
+		for (int i = 0; i < R; i++) {
+			for (int j = 0; j < C; j++) {
+				if (arr[i][j] == 'J') {
+					time[i][j] = 0;
+					q.offer(new int[] {i, j});
+				} else {
+					time[i][j] = -1;
+				}
+			}
+		}
+
+		while (!q.isEmpty()) {
+			int[] tmp = q.poll();
+			int r = tmp[0];
+			int c = tmp[1];
+			for (int i = 0; i < 4; i++) {
+				int nr = r + dr[i];
+				int nc = c + dc[i];
+				if (nr < 0 || nr >= R || nc < 0 || nc >= C) {
+					// 탈출
+					return time[r][c] + 1;
+				}
+				if (arr[nr][nc] != '.') { continue; }
+				if (time[nr][nc] > -1) { continue; }
+				// 불이 번진 시간보다 작아야 해당 칸으로 이동할 수 있다.
+				if (fireTime[nr][nc] == -1 || fireTime[nr][nc] > time[r][c] + 1) {
+					time[nr][nc] = time[r][c] + 1;
+					q.offer(new int[] {nr, nc});
+				}
+			}
+		}
+		return -1;
+	}
+
+	static void setFireTime( ) { // 불이 번지는 시간을 기록한다.
+		fireTime = new int[R][C];
+		Queue<int[]> q = new ArrayDeque<>();
+		for (int i = 0; i < R; i++) {
+			for (int j = 0; j < C; j++) {
+				if (arr[i][j] == 'F') {
+					q.offer(new int[] {i, j});
+					fireTime[i][j] = 0;
+				} else {
+					fireTime[i][j] = -1;
+				}
+			}
+		}
+		while (!q.isEmpty()) {
+			int[] tmp = q.poll();
+			int r = tmp[0];
+			int c = tmp[1];
+			for (int i = 0; i < 4; i++) {
+				int nr = r + dr[i];
+				int nc = c + dc[i];
+				if (nr < 0 || nr >= R || nc < 0 || nc >= C) { continue; }
+				if (arr[nr][nc] == '#') { continue; }
+				if (fireTime[nr][nc] > -1) { continue; }
+				fireTime[nr][nc] = fireTime[r][c] + 1;
+				q.offer(new int[] {nr, nc});
+			}
+		}
+	}
+
+	static void input() throws IOException {
+		StringTokenizer st = new StringTokenizer(br.readLine());
+		R = Integer.parseInt(st.nextToken());
+		C = Integer.parseInt(st.nextToken());
+		arr = new char[R][C];
+		for (int i = 0; i < R; i++) {
+			arr[i] = br.readLine().toCharArray();
+		}
+		br.close();
+	}
+
+}
+```