又是一道Bellman-ford练手，我感觉poj的服务器不是很稳定，一次wa,做了点无伤大雅的改动说我超时，过了一会儿又提交的时候说是CE,然后我加了两个初始化之后就ac了。

还是贴代码：

#include <iostream>
#include <vector>
#include <string>
#include <map>
using namespace std;
struct edge{
    string cu1;
    string cu2;
    
    double rate;
    edge(string s1,string s2,double d){
        cu1=s1; cu2=s2; rate=d;
    }
};
vector<edge> collection_edges;
map<string,double> money;
int num_edges=0;
int num_currencies=0;
bool relax(int i){
    bool flag=true;
    double m1=money[collection_edges[i].cu1];
    double m2=money[collection_edges[i].cu2];
    if(m2<m1*collection_edges[i].rate){
        money[collection_edges[i].cu2]=m1*collection_edges[i].rate;
        flag=false;
    }
    return flag;
    
}

bool bellman_ford(){
    for(int m=0;m<num_currencies-1;m++){
        for(int i=0;i<num_edges;i++){
            relax(i);
        }
    }
    
    for(int i=0;i<num_edges;i++){
        if(money[collection_edges[i].cu2]<money[collection_edges[i].cu1]*collection_edges[i].rate)
            return true;
    }
    return false;
}

int main(int argc, const char * argv[]) {
    int no_case=1;
    while(cin>>num_currencies){
        if(num_currencies==0)
            break;
        
        
        for(int i=0;i<num_currencies;i++){
            string name;
            cin>>name;
            money.insert(pair<string,double>(name,0.0));
        }
        
        cin>>num_edges;
        
        for(int i=0;i<num_edges;i++){
            string name1,name2;
            double r=0;
            cin>>name1>>r>>name2;
            edge e(name1,name2,r);
            collection_edges.push_back(e);
        }
        
        money[collection_edges[0].cu1]=1.0;
        if(bellman_ford()) cout<<"Case "<<no_case<<": Yes"<<endl;
        else cout<<"Case "<<no_case<<": No"<<endl;
        collection_edges.clear();
        money.clear();
        no_case++;
    }
    
    return 0;
}