kuangbin_ShortPathI (POJ 2240)

#include <iostream>
#include <cstring>
#include <string>
#include <queue>
#include <map>
#include <algorithm>
using namespace std;

map<string, int> mapp;
double val[40][40];
int n, m;

bool spfa(int s)
{
    double dis[40];
    bool vis[40];
    int time[40];
    memset(dis, 0, sizeof dis);
    memset(vis, 0, sizeof vis);
    memset(time, 0, sizeof time);

    queue<int> q;
    dis[s] = 1.0;
    vis[s] = true;
    q.push(s);
    while(!q.empty()){
        int u = q.front();
        q.pop();
        vis[u] = false;
        for(int i = 1; i <= n; i++){
            if(dis[i] < dis[u] * val[u][i]){
                dis[i] = dis[u] * val[u][i];
                if(!vis[i]){
                    vis[i] = true;
                    q.push(i);
                    if(++time[i] >= n) return true;
                }
            }
        }
    }
    return false;
}
int main()
{
    int kase = 0;
    while(1){
        cin >> n;
        if(n == 0) break;
        memset(val, 0, sizeof val);
        for(int i = 1; i <= n; i++){
            string str;
            cin >> str;
            mapp[str] = i;
        }
        cin >> m;
        for(int i = 1; i <= m; i++){
            string str1, str2;
            double value;
            cin >> str1 >> value >> str2;
            val[mapp[str1]][mapp[str2]] = value;
        }
        if(spfa(1)) cout << "Case " << ++kase << ": Yes" << endl;
        else cout << "Case " << ++kase << ": No" << endl;
    }
    return 0;
}