【最小割】【bzoj 3774】: 最优选择

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http://www.lydsy.com/JudgeOnline/problem.php?id=3774
tm这最小割能考到这么变态是一种境界
//#define _TEST _TEST#include <cstdio>#include <cstring>#include <cstdlib>#include <iostream>#include <cmath>#include <algorithm>using namespace std;/************************************************Code By willinglive    Blog:http://willinglive.cf************************************************/#define rep(i,l,r) for(int i=(l),___t=(r);i<=___t;i++)#define per(i,r,l) for(int i=(r),___t=(l);i>=___t;i--)#define MS(arr,x) memset(arr,x,sizeof(arr))#define LL long long#define INE(i,u,e) for(int i=head[u];~i;i=e[i].next)inline const int read(){int r=0,k=1;char c=getchar();for(;c<'0'||c>'9';c=getchar())if(c=='-')k=-1;for(;c>='0'&&c<='9';c=getchar())r=r*10+c-'0';return k*r;}/////////////////////////////////////////////////const int inf=0x3f3f3f3f;const int N=6000;const int M=8*N;int n,m;int a[51][51],b[51][51];struct edge{int v,flow,cap,next;}e[M];int head[N],k;int S,T;int cur[N],d[N],q[N];  int di[]={0,0,1,-1};int dj[]={1,-1,0,0};/////////////////////////////////////////////////inline int enc(int x,int y,bool b){return ((x-1)*m+y)<<1|b;}void adde(int u,int v,int f){e[k].v=v;e[k].flow=0;e[k].cap=f;e[k].next=head[u];head[u]=k++;}  void ins(int u,int v,int f1,int f2){adde(u,v,f1);adde(v,u,f2);}  inline int F(int i){return e[i].cap-e[i].flow;}  bool bfs()  {      MS(d,-1); d[q[0]=S]=0; memcpy(cur,head,sizeof(cur));      for(int u,v,l=0,r=1;l<r;)      {          u=q[l++];          INE(i,u,e) if(F(i)&&d[v=e[i].v]==-1)          {              q[r++]=v; d[v]=d[u]+1;              if(v==T) return 1;          }      }      return 0;  }  int dfs(int u,int a)  {      if(u==T||a==0) return a;      for(int &i=cur[u];~i;i=e[i].next) if(F(i)&&d[e[i].v]==d[u]+1)      {          if(int t=dfs(e[i].v,min(a,F(i))))          {              e[i].flow+=t; e[i^1].flow-=t;              return t;          }      }      return 0;  }  int dinic()  {      int f=0;      while(bfs()) while(int t=dfs(S,inf)) f+=t;      return f;  }  /////////////////////////////////////////////////void input(){MS(head,-1);    n=read(); m=read();    rep(i,1,n) rep(j,1,m) a[i][j]=read();    rep(i,1,n) rep(j,1,m) b[i][j]=read();}void solve(){S=enc(n,m,1)+1; T=S+1;rep(i,1,n) rep(j,1,m){if((i+j)&1){ins(S,enc(i,j,0),a[i][j],0);ins(enc(i,j,0),enc(i,j,1),b[i][j],0);}else{ins(enc(i,j,0),T,a[i][j],0);ins(enc(i,j,1),enc(i,j,0),b[i][j],0);}rep(k,0,3){int ni=i+di[k],nj=j+dj[k];if(ni<1||ni>n||nj<1||nj>m) continue;if((i+j)&1) ins(enc(i,j,1),enc(ni,nj,0),inf,0);else ins(enc(ni,nj,0),enc(i,j,1),inf,0);}}int s=0;rep(i,1,n) rep(j,1,m) s+=b[i][j];cout<<s-dinic()<<endl;}/////////////////////////////////////////////////int main(){    #ifndef _TEST    freopen("std.in","r",stdin); freopen("std.out","w",stdout);    #endif    input(),solve();    return 0;}
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