P1522 [USACO2.4]牛的旅行 Cow Tours

R53816523

Luogu/problem/P1522/P1522.cpp

@@ -0,0 +1,52 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, t;
+double g[155][155], d[155], l1, l2 = 1e9, ans;
+pair<int, int> m[155];
+
+double dis(pair<int, int> a, pair<int, int> b) {
+    return sqrt(pow(a.first - b.first, 2) + pow(a.second - b.second, 2));
+}
+
+int main() {
+    cin >> n;
+    for (int i = 1; i <= n; i++) {
+        cin >> m[i].first >> m[i].second;
+    }
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) {
+            scanf("%1d", &t);
+            if (t) {
+                g[i][j] = dis(m[i], m[j]);
+            } else {
+                g[i][j] = i == j ? 0 : 1e9;
+            }
+        }
+    }
+    for (int k = 1; k <= n; k++) {
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= n; j++) {
+                g[i][j] = min(g[i][j], g[i][k] + g[k][j]);
+            }
+        }
+    }
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) {
+            if (g[i][j] != 1e9) {
+                d[i] = max(g[i][j], d[i]);
+            }
+            l1 = max(l1, d[i]);
+        }
+    }
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) {
+            if (g[i][j] == 1e9) {
+                l2 = min(l2, d[i] + dis(m[i], m[j]) + d[j]);
+            }
+        }
+    }
+    cout << fixed << setprecision(6) << max(l1, l2) << endl;
+    return 0;
+}