[20250822] BOJ / G3 / 연구소 3 / 김민진

zinnnn37/202508/22 BOJ G3 연구소 3.md

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+```java
+import java.awt.Point;
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Queue;
+import java.util.StringTokenizer;
+
+public class BJ_17142_연구소_3 {
+
+    private static final int[] dx = {0, 1, 0, -1};
+    private static final int[] dy = {1, 0, -1, 0};
+
+    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;
+    private static int M;
+    private static int ans;
+    private static int virusCnt;
+
+    private static int[][] matrix;
+    private static int[] activeVirus;
+    private static List<Point> virus;
+    private static Queue<Node> q;
+    private static boolean[][] visited;
+
+    private static class Node {
+        int x;
+        int y;
+        int cnt;
+
+        public Node(int x, int y, int cnt) {
+            this.x = x;
+            this.y = y;
+            this.cnt = cnt;
+        }
+    }
+
+    public static void main(String[] args) throws IOException {
+        init();
+        sol();
+    }
+
+    private static void init() throws IOException {
+        st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        ans = Integer.MAX_VALUE;
+
+        matrix = new int[N][N];
+        virus = new ArrayList<>();
+        int v = 0;
+        for (int i = 0; i < N; i++) {
+            st = new StringTokenizer(br.readLine());
+            for (int j = 0; j < N; j++) {
+                matrix[i][j] = Integer.parseInt(st.nextToken());
+
+                if (matrix[i][j] == 2) {
+                    virus.add(new Point(i, j));
+                }
+            }
+        }
+        virusCnt = virus.size();
+        activeVirus = new int[M];
+
+        q = new ArrayDeque<>();
+        visited = new boolean[N][N];
+    }
+
+    private static void sol() throws IOException {
+        perm(0, 0);
+
+        bw.write(ans == Integer.MAX_VALUE ? "-1" : ans + "");
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    private static void perm(int depth, int n) {
+        if (depth == M) {
+            bfs();
+            return;
+        }
+
+        for (int i = n; i < virusCnt; i++) {
+            activeVirus[depth] = i;
+            perm(depth + 1, i + 1);
+        }
+    }
+
+    private static void bfs() {
+        // clear queue and visited
+        clear();
+
+        // put active virus
+        for (int i = 0; i < M; i++) {
+            Point curVirus = virus.get(activeVirus[i]);
+            q.offer(new Node(curVirus.x, curVirus.y, 0));
+            visited[curVirus.x][curVirus.y] = true;
+        }
+
+        int res = 0;
+        while (!q.isEmpty()) {
+            Node cur = q.poll();
+            if (matrix[cur.x][cur.y] == 0) {
+                res = Math.max(res, cur.cnt);
+            }
+
+            for (int d = 0; d < 4; d++) {
+                int nx = cur.x + dx[d];
+                int ny = cur.y + dy[d];
+
+                if (OOB(nx, ny) || visited[nx][ny] || matrix[nx][ny] == 1) {
+                    continue;
+                }
+
+                visited[nx][ny] = true;
+                q.offer(new Node(nx, ny, cur.cnt + 1));
+            }
+        }
+        if (checkValid()) {
+            ans = Math.min(ans, res);
+        }
+    }
+
+    private static void clear() {
+        q.clear();
+
+        for (int i = 0; i < N; i++) {
+            Arrays.fill(visited[i], false);
+        }
+    }
+
+    private static boolean checkValid() {
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < N; j++) {
+                if (matrix[i][j] == 0 && !visited[i][j]) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
+    private static boolean OOB(int x, int y) {
+        return x < 0 || x >= N || y < 0 || y >= N;
+    }
+
+}
+```