P1931 套利

R53832080

Luogu/problem/P1931/P1931.cpp

@@ -0,0 +1,46 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, m, c;
+double w, g[35][35];
+map<string, int> kv;
+string s, s1, s2;
+
+bool floyd() {
+    for (int k = 1; k <= n; k++) {
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= n; j++) {
+                g[i][j] = max(g[i][j], g[i][k] * g[k][j]);
+            }
+        }
+    }
+    for (int i = 1; i <= n; i++) {
+        if (g[i][i] > 1) {
+            return true;
+        }
+    }
+    return false;
+}
+
+int main() {
+    while (cin >> n, n) {
+        kv.clear();
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= n; j++) {
+                g[i][j] = i == j ? 1 : 0;
+            }
+        }
+        for (int i = 1; i <= n; i++) {
+            cin >> s;
+            kv[s] = i;
+        }
+        cin >> m;
+        for (int i = 1; i <= m; i++) {
+            cin >> s1 >> w >> s2;
+            g[kv[s1]][kv[s2]] = w;
+        }
+        cout << "Case " << ++c << ": " << (floyd() ? "Yes" : "No") << endl;
+    }
+    return 0;
+}