BZOJ3876: [Ahoi2014]支线剧情

有下界最小费用可行流。建图可以优化，我没优化。

#include<algorithm>
#include<cstdio>
#include<cstring>
using std::min;
const int inf=1061109567;
const int N=305;
const int s=N-1;
const int t=N-2;
int n,z
,q[N*N],c
,d
;
struct edge{
int v,w,f;edge*s;
}e[N*N];
edge*a=e,*h
;
void ins(int u,int v,int w,int f){
edge s={v,w,f,h[u]};
edge t={u,-w,0,h[v]};
*(h[u]=a++)=s;
*(h[v]=a++)=t;
}
bool spfa(){
memset(c,63,sizeof c);
memset(d,0,sizeof d);
c[q[0]=t]=0;
for(int a=0,b=0;a<=b;++a){
int u=q[a];
z[u]=0;
for(edge*i=h[u];i;i=i->s)
if(e[i-e^1].f&&c[u]-i->w<c[i->v]){
c[i->v]=c[u]-i->w;
d[i->v]=d[u]+1;
if(!z[i->v]++)
q[++b]=i->v;
}
}
return c[s]!=inf;
}
int dfs(int u,int v){
if(u==t)return v;
int s=v;
for(edge*i=h[u];i;i=i->s)
if(c[i->v]==c[u]-i->w&&d[i->v]==d[u]-1&&i->f){
int j=dfs(i->v,min(i->f,s));
i->f-=j,s-=j;
e[i-e^1].f+=j;
if(!s)break;
}
if(s==v)c[u]=inf;
return v-s;
}
int main(){
scanf("%d",&n);
for(int i=1;i<=n;++i){
int j,v,w;
scanf("%d",&j);
ins(i,t,0,j);
ins(i,1,0,inf);
while(j--){
scanf("%d%d",&v,&w);
ins(s,v,w,1);
ins(i,v,w,inf);
}
}
int k=0;
while(spfa())
while(int j=dfs(s,inf))
k+=j*c[s];
printf("%d\n",k);
}