P4043 [AHOI2014/JSOI2014]支线剧情 上下界费用流

#include<bits/stdc++.h>
using namespace std;
//input by bxd
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define repp(i,a,b) for(int i=(a);i>=(b);--i)
#define RI(n) scanf("%d",&(n))
#define RII(n,m) scanf("%d%d",&n,&m)
#define RIII(n,m,k) scanf("%d%d%d",&n,&m,&k)
#define RS(s) scanf("%s",s);
#define ll long long
#define pb push_back
#define inf 0x3f3f3f3f
#define CLR(A,v)  memset(A,v,sizeof A)
//////////////////////////////////
const int N=100001;

ll maxflow,mincost;
int last[N],pre[N],dis[N],flow[N],d[N];
bool vis[N];
struct Edge{
    int next,to,flow,dis;
}edge[N<<1];
int pos=1,head[N];
void init()
{
    pos=1;
    CLR(head,0);
    mincost=maxflow=0;
}
queue <int> q;
inline void add(int from,int to,int flow,int dis)//flow流量 dis费用
{
    edge[++pos].next=head[from];
    edge[pos].flow=flow;
    edge[pos].dis=dis;
    edge[pos].to=to;
    head[from]=pos;

    edge[++pos].next=head[to];
    edge[pos].flow=0;
    edge[pos].dis=-dis;
    edge[pos].to=from;
    head[to]=pos;

}
void ins(int x,int y,int down,int up,int cost)
{
    add(x,y,up-down,cost);
    d[x]-=down;
    d[y]+=down;
}

bool spfa(int s,int t)
{
    CLR(dis,0x3f);
    CLR(flow,0x3f);
    CLR(vis,0);
    while (!q.empty()) q.pop();
    dis[s]=0; pre[t]=-1; q.push(s); vis[s]=1;
    int tot=0;
    while (!q.empty())
    {
        int now=q.front(); q.pop(); vis[now]=0;
        for (int i=head[now]; i; i=edge[i].next)
        {
            int to=edge[i].to;
            if  (edge[i].flow>0 && dis[to]>dis[now]+edge[i].dis)
            {
                dis[to]=edge[i].dis+dis[now];
                flow[to]=min(edge[i].flow,flow[now]);
                last[to]=i;
                pre[to]=now;
                if (!vis[to])
                {
                    q.push(to); vis[to]=1;
                }
            }
        }
    }
    return pre[t]!=-1;
}
inline void MCMF(int s,int t)
{
    while (spfa(s,t))
    {
        int now=t;
        maxflow+=flow[t];
        mincost+=flow[t]*dis[t];
        while (now!=s)
        {
            edge[last[now]].flow-=flow[t];//dis . flow
            edge[last[now]^1].flow+=flow[t];
            now=pre[now];
        }
    }
}
int n,m,s,t,ss,x,a,b,S,T;

int main()
{
    scanf("%d",&n);
    s=n+1;t=s+1;S=t+1;T=S+1;

    ins(s,1,0,inf,0);
    int sum=0;
    rep(i,1,n)
    {
        ins(i,t,0,inf,0);
        int k;scanf("%d",&k);
        while(k--)
        {
            scanf("%d%d",&a,&b);sum+=b;
            ins(i,a,1,inf,b);
        }
    }
    ins(t,s,0,inf,0);

    rep(i,1,t)
    if(d[i]>0)add(S,i,d[i],0);
    else if(d[i]<0)add(i,T,-d[i],0);
    MCMF(S,T);

    cout<<mincost+sum;

    return 0;
}