ZOJ 1654 Place the Robots

04年论文题《黄源河--浅谈图论模型的建立与应用》

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
const int inf=1e9;
struct Edge{int to,next,v;}e[200005];
int head[5005],cnt,d[5005];
void ins(int u,int v,int w){
	e[++cnt]=(Edge){v,head[u],w};head[u]=cnt;
}
void insert(int u,int v,int w){
	ins(u,v,w);ins(v,u,0);
}
bool bfs(int s,int t){
	memset(d,-1,sizeof(d));
	d[s]=0;queue<int>q;q.push(s);
	while(!q.empty()){
		int u=q.front();q.pop();
		for(int i=head[u];i;i=e[i].next)
		if(e[i].v&&d[e[i].to]==-1){
			d[e[i].to]=d[u]+1;
			q.push(e[i].to);
		}
	}
	return d[t]!=-1;
}
int dfs(int x,int f,int t){
	if(x==t)return f;
	int w,flow=0;
	for(int i=head[x];i;i=e[i].next)
	if(e[i].v&&d[e[i].to]==d[x]+1){
		w=dfs(e[i].to,min(f-flow,e[i].v),t);
		e[i].v-=w;e[i^1].v+=w;flow+=w;
		if(flow==f)return f;
	}
	if(!flow)d[x]=-1;
	return flow;
}
int dinic(int s,int t){int ans=0;while(bfs(s,t))ans+=dfs(s,inf,t);return ans;}
int id1[55][55],id2[55][55],tot1,tot2;
void init(){
	memset(head,0,sizeof(head));cnt=1;
	memset(id1,0,sizeof(id1));
	memset(id2,0,sizeof(id2));
	tot1=tot2=0;
}
char mp[55][55];
int main(){
	//freopen("a.in","r",stdin);
	int cas;scanf("%d",&cas);
	for(int kase=1;kase<=cas;kase++){
		int n,m;scanf("%d%d",&n,&m);
		for(int i=1;i<=n;i++)
		scanf("%s",mp[i]+1);
		init();
		for(int i=1;i<=n;i++)
		for(int j=1;j<=m;j++)
		if(mp[i][j]!='#'){
			bool flag=false;
			int now=j;
			while(now<=m&&mp[i][now]!='#')if(mp[i][now++]=='o')flag=true;
			if(flag){
				tot1++;
				while(j<=m&&mp[i][j]!='#')id1[i][j++]=tot1;
			}
		}
		for(int j=1;j<=m;j++)
		for(int i=1;i<=n;i++)
		if(mp[i][j]!='#'){
			bool flag=false;
			int now=i;
			while(now<=n&&mp[now][j]!='#')if(mp[now++][j]=='o')flag=true;
			if(flag){
				tot2++;
				while(i<=n&&mp[i][j]!='#')id2[i++][j]=tot2;
			}
		}
		int S=0,T=tot1+tot2+1;
		for(int i=1;i<=tot1;i++)insert(S,i,1);
		for(int i=1;i<=tot2;i++)insert(i+tot1,T,1);
		for(int i=1;i<=n;i++)
		for(int j=1;j<=m;j++)
		if(mp[i][j]=='o'&&id1[i][j]&&id2[i][j])
		insert(id1[i][j],id2[i][j]+tot1,1);
		printf("Case :%d\n%d\n",kase,dinic(S,T));
	}
	return 0;
}