B - Light It Up

https://atcoder.jp/contests/abc255/submissions/32381074

AtCoder/ABC255/B/B.cpp

@@ -0,0 +1,61 @@
+#include <iostream>
+#include <cmath>
+#include <iomanip>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1005;
+
+int n, k, a[N];
+bool has[N];
+std::pair<int, int> points[N];
+double dis[N][N], dist[N], ans;
+
+double getdis(std::pair<int, int> a, std::pair<int, int> b) {
+    return std::sqrt(1ll * (a.first - b.first) * (a.first - b.first) + 1ll * (a.second - b.second) * (a.second - b.second));
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> k;
+
+    for (int i = 1; i <= k; i++) {
+        cin >> a[i];
+        has[a[i]] = true;
+    }
+
+    for (int i = 1; i <= n; i++) {
+        cin >> points[i].first >> points[i].second;
+    }
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j < i; j++) {
+            dis[i][j] = dis[j][i] = getdis(points[i], points[j]);
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        if (!has[i]) {
+            dist[i] = 9999999999;
+            for (int j = 1; j <= n; j++) {
+                if (i != j) {
+                    if (has[j]) {
+                        dist[i] = std::min(dist[i], dis[i][j]);
+                    }
+                }
+            }
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        ans = std::max(ans, dist[i]);
+    }
+
+    cout << std::fixed << std::setprecision(10) << ans << endl;
+
+    return 0;
+}