[20250412] BOJ G3 연구소 3 이강현

lkhyun/202504/12 BOJ G3 연구소 3.md

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+```java
+import java.util.*;
+import java.io.*;
+
+public class Main {
+    static class Node {
+        int i, j,time;
+
+        public Node(int i, int j, int time) {
+            this.i = i;
+            this.j = j;
+            this.time = time;
+        }
+    }
+
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    static StringTokenizer st;
+    static int N;
+    static int M;
+    static int[][] matrix;
+    static List<Node> virus = new ArrayList<>();
+    static List<Node> selected = new ArrayList<>();
+    static int[] di = {0, 0, -1, 1};
+    static int[] dj = {-1, 1, 0, 0};
+    static int min = Integer.MAX_VALUE;
+    static int zeroCnt = 0;
+
+    public static void main(String[] args) throws Exception {
+        st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        matrix = new int[N][N];
+
+        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 Node(i, j,0));
+                }else if(matrix[i][j] == 0){
+                    zeroCnt++;
+                }
+            }
+        }
+        combination(0, 0);
+        if(min == Integer.MAX_VALUE) bw.write("-1");
+        else bw.write(min + "");
+        bw.close();
+    }
+
+    public static void combination(int start, int count) {
+        if (count == M) {
+            BFS();
+            return;
+        }
+
+        for (int i = start; i < virus.size(); i++) {
+            selected.add(virus.get(i));
+            combination(i + 1, count + 1);
+            selected.remove(selected.size() - 1);
+        }
+    }
+
+    public static void BFS() {
+        PriorityQueue<Node> pq = new PriorityQueue<>((a,b) -> a.time - b.time);
+        int[][] dist = new int[N][N];
+        for (int i = 0; i < N; i++) {
+            Arrays.fill(dist[i],Integer.MAX_VALUE);
+        }
+        for (Node temp : selected) {
+            pq.add(temp);
+            dist[temp.i][temp.j] = 0;
+        }
+        int maxTime = 0;
+        int remainZero = zeroCnt;
+
+        while (!pq.isEmpty()) {
+            Node cur = pq.poll();
+            if (matrix[cur.i][cur.j] == 0) remainZero--;
+            if (remainZero == 0) {
+                maxTime = Math.max(maxTime, cur.time);
+                min = Math.min(min,maxTime);
+                return;
+            }
+            if(dist[cur.i][cur.j] < cur.time) continue;
+            for (int k = 0; k < 4; k++) {
+                int newi = cur.i + di[k];
+                int newj = cur.j + dj[k];
+
+                if (newi < 0 || newi >= N || newj < 0 || newj >= N || matrix[newi][newj] == 1)
+                    continue;
+
+                if (dist[newi][newj] > cur.time + 1) {
+                    pq.add(new Node(newi, newj, cur.time + 1));
+                    dist[newi][newj] = cur.time + 1;
+                }
+            }
+
+        }
+    }
+}
+
+
+```