【bzoj3876】支线剧情

#include<bits/stdc++.h>
#define maxn 405
#define maxm 100005
#define INF 0x7f7f7f7f

using namespace std;

inline int read(){
    int x=0,f=1;char ch=getchar();
    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
    return x*f;
}

struct scsc{
    int next,from,to,w,c;
}edge[maxm<<1];

int Len,head[maxn],ind[maxn],otd[maxn],Sum;

void addedge(int u,int v,int w,int c){
    edge[++Len].to=v;edge[Len].from=u;edge[Len].w=w;edge[Len].c=c;edge[Len].next=head[u];head[u]=Len;
    edge[++Len].to=u;edge[Len].from=v;edge[Len].w=0;edge[Len].c=-c;edge[Len].next=head[v];head[v]=Len;
}

int vis[maxn],d[maxn];

int spfa(int s,int t){
    queue<int>Q;
    for(int i=s;i<=t;++i)vis[i]=0;
    for(int i=s;i<=t;++i)d[i]=INF;
    Q.push(s);vis[s]=1;d[s]=0;
    while(!Q.empty()){
        int u=Q.front();Q.pop();
        for(int i=head[u];i;i=edge[i].next){
            int v=edge[i].to;
            if(edge[i].w&&d[v]>d[u]+edge[i].c){
                d[v]=d[u]+edge[i].c;
                if(!vis[v]){
                    vis[v]=1;
                    Q.push(v);
                }
            }
        }
        vis[u]=0;
    }
    return d[t]!=INF;
}

int ans=0;

int dfs(int u,int f,int t){
    vis[u]=1;
    if(u==t)return f;
    int used=0,w;
    for(int i=head[u];i&&used<f;i=edge[i].next){
        int v=edge[i].to;
        if(edge[i].w&&d[v]==d[u]+edge[i].c&&!vis[v]){
            w=dfs(v,min(f-used,edge[i].w),t);
            edge[i].w-=w;
            edge[i^1].w+=w;
            used+=w;
            ans+=edge[i].c*w;
        }
    }
    return used;
}

void mcmf(int s,int t){
    while(spfa(s,t)){
        vis[t]=1;
        while(vis[t]){
            for(int i=s;i<=t;++i)vis[i]=0;
            dfs(s,INF,t);
        }
    }
}

int n;

int main(){
    n=read();int f1,f2;
    int S=0,T=n+1;Len=1;
    for(int i=1;i<=n;++i){
        otd[i]=read();
        for(int j=1;j<=otd[i];++j){
            f1=read();f2=read();
            ++ind[f1];Sum+=f2;
            addedge(i,f1,INF,f2);
        }
    }
    for(int i=2;i<=n;++i)addedge(i,1,INF,0);
    for(int i=2;i<=n;++i){
        int du=ind[i]-otd[i];
        if(du>0)addedge(S,i,du,0);
        else addedge(i,T,-du,0);
    }
    mcmf(S,T);
    printf("%d\n",ans+Sum);
    return 0;
}