Arbitrage POJ 2240

#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <cstdlib>
#include <cstring>
#include <map>
#include <queue>
using namespace std;

#define maxn 150
#define INF 0x3f3f3f3f
int head[maxn], v[maxn];
double dist[maxn];
int cnt;

struct node
{
    int u, v, next;
    double w;
} maps[maxn];

void Add(int u, int v, double w)
{
    maps[cnt].v = v;
    maps[cnt].w = w;
    maps[cnt].next = head[u];
    head[u] = cnt ++;
}

int spfa(int s)
{
    memset(v, 0, sizeof(v));
    queue<int>Q;
    Q.push(s);
    v[s] = 1;

    while(Q.size())
    {
        int p=Q.front();
        Q.pop();
        v[p] = 0;

        for(int i=head[p]; i!=-1; i=maps[i].next)
        {
            int q = maps[i].v;

            double t = dist[p]*maps[i].w;

            if(dist[q]<t)
            {
                dist[q] = t;
                if(!v[q])
                {
                    v[q] = 1;
                    Q.push(q);
                }
            }
        }

        if(dist[s] > 1)
        return 1;

    }

    return 0;
}

int main()
{
    int n, m, t=1;
    char str[50];

    while(scanf("%d", &n), n)
    {
        map<string, int>s;
        s.clear();

        for(int i=1; i<=n; i++)
        {
            scanf("%s", str);
            s[str] = i;
        }

        scanf("%d", &m);

        char a[50], b[50];
        double c;
        cnt = 0;
        memset(head, -1, sizeof(head));

        for(int i=1; i<=m; i++)
        {
            scanf("%s %lf %s", a, &c, b);
            Add(s[a], s[b], c);
        }

        int ans = 0;
        for(int i=1; i<=n; i++)
        {
            for(int j=1; j<=n; j++)
                dist[j] = - INF;
            dist[i] = 1;
            ans += spfa(i);
            if(ans)
                break;
        }

        if(ans)  printf("Case %d: Yes\n", t++);
        else printf("Case %d: No\n", t++);

    }


    return 0;
}