HDU 1217 Arbitrage 最短路

floyed算法的变形。

#include<iostream>
#include<cstdio>
#include<string.h>
#include<algorithm>
#include<queue>
#include<map>
#include<string>
using namespace std;

int e,cnt,n,m;
double dis[40][40];
map<string,int> mapp;

int main()
{
    int cas=0;
    while (~scanf("%d",&n) && n)
    {
        cnt=0; cas++;
        mapp.clear();
        memset(dis,0,sizeof(dis));
        for (int i=1; i<=n; i++)
        {
            cnt++;
            string str; cin>>str;
            mapp[str]=cnt;
            dis[i][i]=1;
        }
        scanf("%d",&m);
        for (int i=1; i<=m; i++)
        {
            string str2,str1; double c;
            cin>>str1; cin>>c; cin>>str2;
            dis[mapp[str1]][mapp[str2]]=c;
            //cout<<"1="<<mapp[str1]<<" 2="<<mapp[str2]<<" c="<<dis[mapp[str1]][mapp[str2]]<<endl;
        }
        for (int k=1; k<=cnt; k++)
        {
            for (int i=1; i<=cnt; i++)
            {
                for (int j=1; j<=cnt; j++)
                {
                    //cout<<"i="<<i<<" k="<<k<<" j="<<j<<endl;
                    //cout<<"dik="<<dis[i][k]<<" dkj="<<dis[k][j]<<endl;
                    if (dis[i][j]<dis[i][k]*dis[k][j])
                    {
                        dis[i][j]=dis[i][k]*dis[k][j];
                    }
                   // cout<<"dij="<<dis[i][j]<<endl;
                }
            }
        }
        bool flag=false;
        for (int i=1; i<=cnt; i++)
        {
            if (dis[i][i]>1)
            {
                flag=true; break;
            }
        }
        if (flag)
        cout<<"Case "<<cas<<": Yes"<<endl;
        else cout<<"Case "<<cas<<": No"<<endl;
    }
    return 0;
}