[20250715] BOJ / G3 / 감시 / 이인희

LiiNi-coder/202507/15 BOJ 감시.md

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+```java
+import java.awt.Point;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.LinkedList;import java.util.Map;
+import java.util.StringTokenizer;
+
+public class B15683 {
+	static class CCTV{
+		int id;
+		Point p;
+		public CCTV(int id, Point p) {
+			this.id = id;
+			this.p = p;
+		}
+	}
+	private static BufferedReader br;
+	private static int m;
+	private static int n;
+	private static LinkedList<int[]> combinations;
+	private static int[] comb;
+	private static ArrayList<B15683.CCTV> cctvs;
+	private static HashSet<Point> walls;
+	private static ArrayDeque<Point> buffer;
+	private static int[][] drdcs = {
+			{0, 1},{1, 0},{0, -1}, {-1, 0}
+	};
+	private static int[][][] indexesDrdcsAtId = {null, {{0}, {1}, {2}, {3}}
+	,{{0, 2}, {1, 3}, {0, 2}, {1, 3}}
+	,{{0, 1}, {1, 2}, {2, 3}, {3, 0}}
+	,{{0, 1, 2}, {1, 2, 3}, {2, 3, 0}, {3, 0, 1}}
+	,{{0, 1, 2, 3}, {0, 1, 2, 3}, {0, 1, 2, 3}, {0, 1, 2, 3}}};
+	private static int[][] map;
+	public static void main(String[] args) throws IOException {
+		br = new BufferedReader(new InputStreamReader(System.in));
+		var tokens = br.readLine().split(" ");
+		n = Integer.parseInt(tokens[0]);
+		m = Integer.parseInt(tokens[1]);
+		walls = new HashSet<Point>();
+		cctvs = new ArrayList<CCTV>();
+		map = new int[n][m];
+		for(int r = 0; r<n; r++) {
+			var st = new StringTokenizer(br.readLine());
+			for(int c = 0; c<m; c++) {
+				String value = st.nextToken();
+				int valueInt = Integer.parseInt(value);
+				map[r][c] = valueInt;
+				if("0".equals(value))
+					continue;
+				if("6".equals(value)) {
+					walls.add(new Point(r, c));
+				}else {
+					cctvs.add(new CCTV(valueInt, new Point(r, c)));
+				}
+			}
+		}
+
+		int nOfZero = n*m - walls.size() - cctvs.size();
+		int answer = nOfZero;
+		for (Iterator iterator = getCombinations().iterator(); iterator.hasNext();) {
+			buffer = new ArrayDeque<Point>();
+			int[] directions = (int[]) iterator.next();
+
+			for(int i = 0; i<directions.length; i++) {
+				int direction = directions[i];
+				//cctvs[i]에서의 direction을 기준으로 map반영
+				fetchMap(cctvs.get(i), direction);
+				//printMap();
+			}
+			answer = Math.min(answer, nOfZero - buffer.size());
+			recoverMap();
+		}
+		System.out.println(answer);
+
+	}
+
+	private static void printMap() {
+		for (int r = 0; r < map.length; r++) {
+			for (int c = 0; c < map[0].length; c++) {
+				System.out.print(map[r][c] + " ");
+			}
+			System.out.println();
+		}
+		System.out.println("------");
+	}
+
+	private static void recoverMap() {
+		while(!buffer.isEmpty()) {
+			Point p = buffer.pollLast();
+			map[p.x][p.y] = 0;
+		}
+
+	}
+
+	private static void fetchMap(CCTV cctv, int direction) {
+		for(int idDrdcs : indexesDrdcsAtId[cctv.id][direction]){
+			int[] drdc = drdcs[idDrdcs];
+			int nr = cctv.p.x;
+			int nc = cctv.p.y;
+
+			while(true) {
+				nr+= drdc[0];
+				nc+= drdc[1];
+				if((nr<0 || nr >= n || nc <0 || nc>=m) || walls.contains(new Point(nr, nc))) {
+					break;
+				}
+				if(map[nr][nc] >= 1 && map[nr][nc] <= 5)
+					continue;
+				map[nr][nc] = cctv.id;
+				buffer.addLast(new Point(nr, nc));
+			}
+
+		}
+	}
+
+	private static LinkedList<int[]> getCombinations() {
+		combinations = new LinkedList<int[]>();
+		comb = new int[cctvs.size()]; 
+		recur(0);
+
+		return combinations;
+	}
+
+	private static void recur(int index) {
+		if(index == cctvs.size()) {
+			combinations.add(comb.clone());
+			return;
+		}
+		for(int i = 0; i<4; i++) {
+			comb[index] = i;
+			recur(index+1);
+		}
+
+	}
+
+}
+```