pku2240 Arbitrage

http://poj.org/problem?id=2240

图论，最短路，SPFA

#include <stdio.h>
#include <string.h>
#include <queue>
#include <string>
#include <map>
#include <iostream>

#define N 123

using namespace std;

int n, m, src;
int x[N], y[N], len[N];
float dist[N];
bool inQue[N];
queue<int> que;
const int inf = 1<<30;
vector<pair<int, float> > g[N];
int count1[N];
float src0 = 10000;

int spfa()
{
    int i;
    for(i=0; i<N; i++)
    {
        inQue[i] = false;
        dist[i] = 0;
        count1[i] = 0;
    }
    dist[src] = src0;
    while(!que.empty())
    {
        que.pop();
    }
    que.push(src);
    count1[src] ++;
    inQue[src] = true;
    while(!que.empty())
    {
        int u = que.front();
        que.pop();
        for(i=0; i<g[u].size(); i++)
        {
            if(dist[u]*g[u][i].second > dist[g[u][i].first])
            {
                dist[g[u][i].first] = dist[u]*g[u][i].second;
                if(!inQue[g[u][i].first])
                {
                    inQue[g[u][i].first] = true;
                    que.push(g[u][i].first);
                    count1[g[u][i].first] ++;
                    if(count1[g[u][i].first] > n)
                    {
                        return -1;
                    }
                }
            }
        }
        inQue[u] = false;
    }
    return 0;
}


int main()
{
    int x, y, cases, i, j;
    float len;
    map<string, int> map1;
    string s, s1, s2;
    for(cases=1; cin >> n, n; cases++)
    {
        printf("Case %d: ", cases);
        map1.clear();
        for(i=1; i<=n; i++)
        {
            g[i].clear();
            cin >> s;
            map1.insert(make_pair(s, i));
        }
        cin >> m;
        for(i=1; i<=m; i++)
        {
            cin >> s1 >> len >> s2;
            x = map1[s1];
            y = map1[s2];
            g[x].push_back(make_pair(y, len));
        }
        src = 1;
        if(spfa() == -1)
        {
            printf("Yes\n");
        }
        else
        {
            if(dist[1] > 10000.0)
            {
                printf("Yes\n");
            }
            else
            {
                printf("No\n");
            }
        }
    }
    return 0;
}