bzoj1412: [ZJOI2009]狼和羊的故事

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
#define rep(i,n) for(int i=1;i<=n;i++)
#define clr(x,c) memset(x,c,sizeof(x))
int read(){
	int x=0;char c=getchar();bool f=true;
	while(!isdigit(c)) {
		if(c==‘-‘) f=false; c=getchar();
	}
	while(isdigit(c)) x=x*10+c-‘0‘,c=getchar();
	return f?x:-x;
} 
int xx[5]={0,0,0,1,-1};
int yy[5]={0,1,-1,0,0};
const int nmax=10005;
const int maxn=100005;
const int inf=0x7f7f7f7f;
struct edge{
	int to,cap;edge *next,*rev;
};
edge edges[maxn],*pt,*head[nmax],*p[nmax],*cur[nmax];
int cnt[nmax],h[nmax],g[105][105];
void add(int u,int v,int d){
	pt->to=v;pt->cap=d;pt->next=head[u];head[u]=pt++;
}
void adde(int u,int v,int d){
	add(u,v,d);add(v,u,0);head[u]->rev=head[v];head[v]->rev=head[u];
}
int maxflow(int s,int t,int n){
	clr(cnt,0);cnt[0]=n;clr(h,0);
	int flow=0,a=inf,x=s;edge *e;
	while(h[s]<n){
		for(e=cur[x];e;e=e->next) if(e->cap>0&&h[x]==h[e->to]+1) break;
		if(e){
			a=min(a,e->cap);p[e->to]=cur[x]=e;x=e->to;
			if(x==t){
				while(x!=s) p[x]->cap-=a,p[x]->rev->cap+=a,x=p[x]->rev->to;
				flow+=a,a=inf;
			}
		}else{
			if(!--cnt[h[x]]) break;
			h[x]=n;
			for(e=head[x];e;e=e->next) if(e->cap>0&&h[x]>h[e->to]+1) h[x]=h[e->to]+1,cur[x]=e;
			cnt[h[x]]++;
			if(x!=s) x=p[x]->rev->to;
		}
	}
	return flow;
}
int main(){
	pt=edges;clr(head,0);
	int n=read(),m=read(),s=0,t=n*m+1;
	rep(i,n) rep(j,m) g[i][j]=read();
	rep(i,n) rep(j,m){
		if(g[i][j]==2)	adde(m*(i-1)+j,t,inf);
		 else if(g[i][j]==1) adde(s,m*(i-1)+j,inf);
	     rep(k,4){
			int tx=i+xx[k],ty=j+yy[k];
			if(tx&&ty&&tx<=n&&ty<=m&&(g[i][j]!=g[tx][ty]||!(g[i][j]|g[tx][ty]))) adde(m*(i-1)+j,m*(tx-1)+ty,1);
		}
	}
	printf("%d\n",maxflow(s,t,t+1));
	return 0;
}