[POJ-3281]
思路:
把牛拆点;
s向食物连边,流量1;
饮料向t连边,流量1;
食物向牛1连边,流量1;
牛2向饮料连边,流量1;
最大流;
来,上代码:
#include <cstdio> #include <cstring> #include <iostream> #include <algorithm> using namespace std; #define maxn 2005 #define INF 0x7fffffff int n,f,d,s,t,head[maxn],E[maxn<<2],V[maxn<<2],F[maxn<<2]; int cnt=1,deep[maxn],que[maxn<<4]; inline void in(int &now) { char Cget=getchar();now=0; while(Cget>‘9‘||Cget<‘0‘) Cget=getchar(); while(Cget>=‘0‘&&Cget<=‘9‘) { now=now*10+Cget-‘0‘; Cget=getchar(); } } inline void edge_add(int u,int v,int f) { E[++cnt]=head[u],V[cnt]=v,F[cnt]=f,head[u]=cnt; E[++cnt]=head[v],V[cnt]=u,F[cnt]=0,head[v]=cnt; } inline bool bfs() { for(int i=s;i<=t;i++) deep[i]=-1; int h=0,tail=1;deep[s]=0,que[h]=s; while(h<tail) { int now=que[h++]; for(int i=head[now];i;i=E[i]) { if(deep[V[i]]<0&&F[i]>0) { deep[V[i]]=deep[now]+1; if(V[i]==t) return true; que[tail++]=V[i]; } } } return false; } int flowing(int now,int flow) { if(flow<=0||now==t) return flow; int oldflow=0; for(int i=head[now];i;i=E[i]) { if(F[i]>0&&deep[V[i]]==deep[now]+1) { int pos=flowing(V[i],min(flow,F[i])); flow-=pos,oldflow+=pos,F[i]-=pos,F[i^1]+=pos; if(flow==0) return oldflow; } } if(oldflow==0) deep[now]=-1; return oldflow; } int main() { in(n),in(f),in(d); int u,v,nf,nd;t=f+n+n+d+1; for(int i=1;i<=f;i++) edge_add(s,i,1); for(int i=1;i<=d;i++) edge_add(f+n+n+i,t,1); for(int i=1;i<=n;i++) { edge_add(f+i,f+n+i,1),in(nf),in(nd); for(int j=1;j<=nf;j++) in(u),edge_add(u,f+i,1); for(int j=1;j<=nd;j++) in(u),edge_add(f+n+i,f+n+n+u,1); } int ans=0; while(bfs()) ans+=flowing(s,INF); cout<<ans; return 0; }
时间: 2024-10-12 09:36:49