[20250820] BOJ / G4 / 가운데에서 만나 / 이준희

Author: JHLEE325

JHLEE325/202508/20 BOJ G4 가운데서 만나기.md

@@ -0,0 +1,82 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static int n, m, k;
+    static int[][] map;
+    static final int INF = 987654321;
+
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+
+        n = Integer.parseInt(st.nextToken());
+        m = Integer.parseInt(st.nextToken());
+
+        map = new int[n][n];
+        for (int i = 0; i < n; i++) {
+            Arrays.fill(map[i], INF);
+            map[i][i] = 0;
+        }
+
+        for (int i = 0; i < m; i++) {
+            st = new StringTokenizer(br.readLine());
+            int from = Integer.parseInt(st.nextToken()) - 1;
+            int to = Integer.parseInt(st.nextToken()) - 1;
+            int cost = Integer.parseInt(st.nextToken());
+            if (cost < map[from][to]) map[from][to] = cost;
+        }
+
+        for (int k = 0; k < n; k++) {
+            for (int i = 0; i < n; i++) {
+                if (map[i][k] == INF) continue;
+                for (int j = 0; j < n; j++) {
+                    if (map[k][j] == INF) continue;
+                    map[i][j] = Math.min(map[i][j], map[i][k] + map[k][j]);
+                }
+            }
+        }
+
+        k = Integer.parseInt(br.readLine());
+        int[] friend = new int[k];
+        st = new StringTokenizer(br.readLine());
+        for (int i = 0; i < k; i++) {
+            friend[i] = Integer.parseInt(st.nextToken()) - 1;
+        }
+
+        int best = INF;
+        ArrayList<Integer> ans = new ArrayList<>();
+
+        for (int v = 0; v < n; v++) {
+            int worst = 0;
+            boolean ok = true;
+            for (int s : friend) {
+                if (map[s][v] == INF || map[v][s] == INF) {
+                    ok = false;
+                    break;
+                }
+                worst = Math.max(worst, map[s][v] + map[v][s]);
+            }
+            if (!ok) continue;
+
+            if (worst < best) {
+                best = worst;
+                ans.clear();
+                ans.add(v + 1);
+            } else if (worst == best) {
+                ans.add(v + 1);
+            }
+        }
+
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < ans.size(); i++) {
+            if (i > 0) sb.append(' ');
+            sb.append(ans.get(i));
+        }
+        System.out.println(sb.toString());
+    }
+}
+
+```