HDOJ 1217 Floyd

#include <iostream>
#include <string>
#include <map>

using namespace std;

map<string, int> edge;
double matrix[30][30];

bool floyd_Arbitrage(int n){
    for (int k = 0; k < n; k++)
        for (int i = 0; i < n; i++)
            for (int j = 0; j < n; j++)
                if (matrix[i][k] * matrix[k][j] - matrix[i][j] > 1e-8)
                    if (i == j)
                        return true;
                    else
                        matrix[i][j] = matrix[i][k] * matrix[k][j];
    return false;
}

int main(){
    int n;
    int count = 0;
    while (cin >> n && n){
        int m;
        count += 1;
        for (int i = 0; i < n; i++)
            for (int j = 0; j < n; j++){
                if (i != j)
                    matrix[i][j] = 0;
                else
                    matrix[i][j] = 1;
            }
        for (int i = 0; i < n; i++){
            string temp;
            cin >> temp;
            edge[temp] = i;
        }
        cin >> m;
        for (int i = 0; i < m; i++){
            string head, tail;
            double temp;
            cin >> head >> temp >> tail;
            matrix[edge[head]][edge[tail]] = temp;
        }
        if (floyd_Arbitrage(n))
            cout << "Case " << count << ": Yes\n";
        else
            cout << "Case " << count << ": No\n";
    }
    return 0;
}