[20251018] BOJ / G3 / 감시 / 김민진

Author: zinnnn37

zinnnn37/202510/18 BOJ G3 감시.md

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+```java
+import java.io.*;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.StringTokenizer;
+
+public class BJ_15683_감시 {
+
+	private static final int[]     dx  = { -1, 1, 0, 0 };
+	private static final int[]     dy  = { 0, 0, -1, 1 };
+	private static final int[][][] dir = {
+			{ { 0 } },
+			{ { 0 }, { 1 }, { 2 }, { 3 } }, // 1번 CCTV
+			{ { 0, 1 }, { 2, 3 } }, // 2번
+			{ { 0, 2 }, { 0, 3 }, { 1, 2 }, { 1, 3 } },
+			{ { 0, 1, 2 }, { 0, 1, 3 }, { 1, 2, 3 }, { 0, 2, 3 } },
+			{ { 0, 1, 2, 3 } }
+	};
+
+	private static final BufferedReader  br = new BufferedReader(new InputStreamReader(System.in));
+	private static final BufferedWriter  bw = new BufferedWriter(new OutputStreamWriter(System.out));
+	private static       StringTokenizer st;
+
+	private static int N, M, res;
+	private static int[][] map;
+
+	private static int        cctvCnt;
+	private static List<CCTV> cctvs = new ArrayList<>();
+
+	static class CCTV {
+		int x;
+		int y;
+		int type;
+
+		public CCTV(int x, int y, int type) {
+			this.x = x;
+			this.y = y;
+			this.type = type;
+		}
+	}
+
+	public static void main(String[] args) throws IOException {
+		init();
+		sol(0, map);
+
+		bw.write(res + "");
+		bw.flush();
+		bw.close();
+		br.close();
+	}
+
+	public static void init() throws IOException {
+		st = new StringTokenizer(br.readLine());
+		N = Integer.parseInt(st.nextToken());
+		M = Integer.parseInt(st.nextToken());
+
+		res = Integer.MAX_VALUE;
+		map = new int[N][M];
+
+		for (int i = 0; i < N; i++) {
+			st = new StringTokenizer(br.readLine());
+
+			for (int j = 0; j < M; j++) {
+				map[i][j] = Integer.parseInt(st.nextToken());
+
+				if (1 <= map[i][j] && map[i][j] <= 5) {
+					cctvs.add(new CCTV(i, j, map[i][j]));
+				}
+			}
+		}
+
+		cctvCnt = cctvs.size();
+	}
+
+	public static void sol(int depth, int[][] prev) {
+		if (depth == cctvCnt) {
+			res = Math.min(res, countBlind(prev));
+			return;
+		}
+
+		int[][] copied = new int[N][M];
+
+		CCTV cur    = cctvs.get(depth);
+		int  type   = cur.type;
+		int  rotate = dir[type].length;
+
+		for (int i = 0; i < rotate; i++) {
+			copy(copied, prev);
+
+			for (int j = 0; j < dir[type][i].length; j++) {
+				countWatched(cur.x, cur.y, dir[type][i][j], copied);
+			}
+
+			sol(depth + 1, copied);
+		}
+	}
+
+	public static int countBlind(int[][] arr) {
+		int blind = 0;
+		for (int i = 0; i < N; i++) {
+			for (int j = 0; j < M; j++) {
+				if (arr[i][j] == 0) {
+					blind++;
+				}
+			}
+		}
+		return blind;
+	}
+
+	public static int countWatched(int x, int y, int dir, int[][] copied) {
+		int cnt = 0;
+		while (true) {
+			x += dx[dir];
+			y += dy[dir];
+
+			if (OOB(x, y) || copied[x][y] == 6) {
+				return cnt;
+			}
+
+			if (copied[x][y] == 0) {
+				cnt++;
+				copied[x][y] = -1;
+			}
+		}
+	}
+
+	public static void copy(int[][] from, int[][] to) {
+		for (int i = 0; i < N; i++) {
+			from[i] = Arrays.copyOf(to[i], M);
+		}
+	}
+
+	private static boolean OOB(int x, int y) {
+		return x < 0 || N <= x || y < 0 || M <= y;
+	}
+}
+```