【POJ 2240】Arbitrage

#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <map>

using namespace std;

map<string, int> ID;
double dis[35][35];
int n, m;

int main()
{
    int kase = 0;
    while (scanf("%d", &n) == 1 && n)
    {
        string s, s1;
        ID.clear();
        for (int i = 0; i < n; ++i)
        {
            cin >> s;
            ID[s] = i;
        }
        for (int i = 0; i < n; ++i)
            for (int j = 0; j < n; ++j)
                dis[i][j] = 1.0;
        scanf("%d", &m);
        for (int i = 0; i < m; ++i)
        {
            double x;
            cin >> s >> x >> s1;
            int id1 = ID[s], id2 = ID[s1];
            dis[id1][id2] = x;
        }
        for (int k = 0; k < n; ++k)
            for (int i = 0; i < n; ++i)
                for (int j = 0; j < n; ++j)
                    dis[i][j] = max(dis[i][j], dis[i][k] * dis[k][j]);
        bool flag = true;
        printf("Case %d: ", ++kase);
        for (int i = 0; i < n; ++i)
            if (dis[i][i] > 1)
            {
                flag = false;
                printf("Yes\n");
                break;
            }
        if (flag) printf("No\n");
    }
    return 0;
}