# poj_2240 Bellman-ford算法变形

#include<iostream>
#include<fstream>
#include<map>

using namespace std;

int n, m;
map<string, int> STL;

char str[50], str1[50], str2[50];
double dist[40], rate;

struct EDGE{
int ci;
int cj;
double cij;
}edges[1000];

bool bellman_ford(int sr)
{
for (int i = 0; i <= n; i++)
dist[i] = 0.0;
dist[sr] = 1.0;
for (int i = 0; i <n; i++)
{
for (int j = 1; j <= m; j++)
{
if (dist[edges[j].cj] < dist[edges[j].ci] * edges[j].cij)
{
dist[edges[j].cj] = dist[edges[j].ci] * edges[j].cij;
}
}
}
if (dist[sr]>1.0)
return true;
else
return false;
}

int main()
{
//ifstream in("text.txt");
int cases = 0;
while (cin >> n && n != 0)
{
cases++;
for (int i = 1; i <= n; i++)
{
cin >> str;
STL[str] = i;
}
cin >> m;
for (int i = 1; i <= m; i++)
{
cin >> str1 >> rate >> str2;
edges[i].ci = STL[str1];
edges[i].cj = STL[str2];
edges[i].cij = rate;
}
int sr;
for (sr= 1; sr <= n; sr++)
{
if (bellman_ford(sr))
break;
}
if (sr<=n)
cout << "Case " << cases << ": Yes" << endl;
else
cout << "Case " << cases << ": No" << endl;
}
//system("pause");
return 0;
}
原文作者：Bellman - ford算法
原文地址: https://blog.csdn.net/yeruby/article/details/38121793
本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。