poj1860Currency Exchange

#include <iostream>
#include <cstring>
#include <stdio.h>

using namespace std;

int n,m,s,all;
double v;
double dis[110];
class exchange_point
{
public:
    int a,b;
    double r,c;
}point[210];
bool BF()
{
    memset(dis,0,sizeof(dis));
    dis[s]=v;
    bool flag;
    for(int i=1;i<=n-1;i++)
    {
        flag=false;
        for(int j=0;j<all;j++)
        {
            if(dis[point[j].b]<(dis[point[j].a]-point[j].c)*point[j].r)
            {
                dis[point[j].b]=(dis[point[j].a]-point[j].c)*point[j].r;
                flag=true;
            }
        }
        if(flag==false)
            break;
    }
        for(int k=0;k<all;k++)
        {
            if(dis[point[k].b]<(dis[point[k].a]-point[k].c)*point[k].r)
            {
                return true;
            }
        }
        return false;
}
int main()
{
    double rab,cab,rba,cba;
    int a,b;
    while(~scanf("%d%d%d%lf",&n,&m,&s,&v))
    {
        all=0;
        for(int i=0;i<m;i++)
        {
            cin>>a>>b>>rab>>cab>>rba>>cba;
            point[all].a=a;
            point[all].b=b;
            point[all].r=rab;
            point[all++].c=cab;
            point[all].a=b;
            point[all].b=a;
            point[all].r=rba;
            point[all++].c=cba;
        }
        if(BF())
            printf("YES
");
        else
            printf("NO
");
    }
    return 0;
}