CSU Double Shortest Paths 湖南省第十届省赛

第二道最小费用最大流，spfa+EK的组合比想象中快很多

开始开边表为点的8倍，RE,不知道为什么

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
using namespace std;
const int maxn=508;
const int INF=0x3f3f3f3f;
struct fuck{
    int u,v,cap,cost,next;
}edge[maxn<<4];
int head[maxn];
int dis[maxn],pre[maxn],vis[maxn];
int tol;
int n;
void init()
{
    tol=0;
    memset(head,-1,sizeof(head));
}
void addedge(int u,int v,int w,int c)
{
    edge[tol].u=u;
    edge[tol].v=v;
    edge[tol].cap=c;
    edge[tol].cost=w;
    edge[tol].next=head[u];
    head[u]=tol++;
    edge[tol].u=v;
    edge[tol].v=u;
    edge[tol].cap=0;
    edge[tol].cost=-w;
    edge[tol].next=head[v];
    head[v]=tol++;
}
bool spfa()
{
    queue<int>    q;
    q.push(0);
    memset(dis,INF,sizeof(dis));
    memset(vis,false,sizeof(vis));
    dis[0]=0;vis[0]=true;pre[0]=-1;
    int i,u,v;
    while(!q.empty())
    {
        u=q.front();q.pop();
        vis[u]=false;
        for(i=head[u];i!=-1;i=edge[i].next)
        {
            v=edge[i].v;
            if(edge[i].cap>0&&dis[v]>dis[u]+edge[i].cost)
            {
                dis[v]=dis[u]+edge[i].cost;
                pre[v]=i;
                if(!vis[v])    q.push(v);
            }
        }
    }
    if(dis[n]>=INF)    return false;
    return true;
}
int min_costflow()
{
    int co,fl,u,i;
    co=fl=0;
    memset(dis,INF,sizeof(dis));
    while(spfa())
    {
        int mi=INF;
        bool flag=true;
        for(i=n;i!=0;i=edge[pre[i]].u)
            mi=min(mi,edge[pre[i]].cap);
        for(i=n;i!=0;i=edge[pre[i]].u)
        {
            edge[pre[i]].cap-=mi;
            edge[pre[i]^1].cap+=mi;
        }
        fl+=mi;
        co+=dis[n];
    }
    return co;
}
int main()
{
    int i,j,m,u,v,w,p;
    int cas=1;
    while(scanf("%d%d",&n,&m)==2)
    {
        init();
        addedge(0,1,0,2);
        for(i=1;i<=m;i++)
        {
            scanf("%d%d%d%d",&u,&v,&w,&p);
            {
                addedge(u,v,w,1);
                addedge(u,v,w+p,1);
            }
        }
        addedge(n,n+1,0,2);
        n++;
        printf("Case %d: %d
",cas++,min_costflow());
    }
    return 0;
}