Dijkstra堆优化模板

priority_queue< pair<ll,ll> >q;
void SPFA(ll top)
{
    memset(bian,0,sizeof(bian));
    dis[top]=0;q.push(make_pair(0,top));bian[top]=1;
    while(!q.empty())
    {
       ll x=q.top().second;q.pop();
       for(ll i=head[x];i;i=e[i].n)
       {
           ll to=e[i].to;
           if(dis[to]>dis[x]+e[i].w)
           {
               dis[to]=dis[x]+e[i].w;
               if(bian[to]==0)
               {
                  q.push(make_pair(-dis[to],to));
                  bian[to]=1;
               }
           }
       }
    }
}