POJ-1860-Currency Exchange

#include<cstdio>
#include<cstring>
#include<iostream>
#include<queue>
using namespace std;
const int maxn=210;
const int maxm=102;
int e,n,m,s,head[maxm],pnt[maxn],nxt[maxn],cnt[maxm];
double v,cost[maxn],com[maxn],dist[maxm];
bool vis[maxm];
queue<int> q;
void AddEdge(int u,int v,double rate,double c)
{
pnt[e]=v;nxt[e]=head[u];cost[e]=rate;com[e]=c;head[u]=e++;
}
bool Spfa(int st,double val)
{
memset(dist,0,sizeof(dist));
memset(vis,0,sizeof(vis));
memset(cnt,0,sizeof(cnt));
while(!q.empty())
q.pop();
dist[st]=val;
cnt[st]=1;
q.push(st);
while(!q.empty())
{
int u=q.front();
q.pop();
vis[u]=0;
for(int i=head[u];i!=-1;i=nxt[i])
{
int v=pnt[i];
if(dist[v]<(dist[u]-com[i])*cost[i])
{
dist[v]=(dist[u]-com[i])*cost[i];
if(!vis[v])
{
vis[v]=1;
q.push(v);
if(++cnt[v]>n)
return true;
}
}
}

}
return false;
}
int main()
{
while(scanf("%d%d%d%lf",&n,&m,&s,&v)!=EOF)
{
memset(head,-1,sizeof(head));
e=0;
for(int i=0;i<m;i++)
{
int u,v;
double x1,y1,x2,y2;
scanf("%d%d%lf%lf%lf%lf",&u,&v,&x1,&y1,&x2,&y2);
AddEdge(u,v,x1,y1);
AddEdge(v,u,x2,y2);
}
if(Spfa(s,v))
printf("YES\n");
else
printf("NO\n");
}
return 0;
}