完全图
最多选择logn个点(下取整)(每选择一个点覆盖至少一半的规模)
暴力O(75^5)(不严格)枚举+bitset
(随机化也可过)
#include<bits/stdc++.h>
#define reg register int
#define il inline
#define int long long
#define numb (ch^'0')
using namespace std;
typedef long long ll;
il void rd(ll &x){
char ch;x=;bool fl=false;
while(!isdigit(ch=getchar()))(ch=='-')&&(fl=true);
for(x=numb;isdigit(ch=getchar());x=x*+numb);
(fl==true)&&(x=-x);
}
namespace Miracle{
const int N=;
int n;
char con[N][N];
bitset<N>to[N],now;
bool c1(){
for(reg a1=;a1<=n;++a1)
if(to[a1].count()==n) return true;
return false;
}
bool c2(){
for(reg a1=;a1<=n;++a1)
for(reg a2=a1+;a2<=n;++a2)
if((to[a1]|to[a2]).count()==n) return true;
return false;
}
bool c3(){
for(reg a1=;a1<=n;++a1)
for(reg a2=a1+;a2<=n;++a2)
for(reg a3=a2+;a3<=n;++a3)
if((to[a1]|to[a2]|to[a3]).count()==n) return true;
return false;
}
bool c4(){
for(reg a1=;a1<=n;++a1)
for(reg a2=a1+;a2<=n;++a2)
for(reg a3=a2+;a3<=n;++a3)
for(reg a4=a3+;a4<=n;++a4)
if((to[a1]|to[a2]|to[a3]|to[a4]).count()==n) return true;
return false;
}
bool c5(){
for(reg a1=;a1<=n;++a1)
for(reg a2=a1+;a2<=n;++a2)
for(reg a3=a2+;a3<=n;++a3)
for(reg a4=a3+;a4<=n;++a4)
for(reg a5=a4+;a5<=n;++a5)
if((to[a1]|to[a2]|to[a3]|to[a4]|to[a5]).count()==n) return true;
return false;
}
int main(){
int o=;
while(scanf("%d",&n)!=EOF){
for(reg i=;i<=n;++i) to[i].reset();
for(reg i=;i<=n;++i){
scanf("%s",con[i]+);
for(reg j=;j<=n;++j){
if(i==j) continue;
if(con[i][j]=='')to[i][j]=;
else to[i][j]=;
}
to[i][i]=;
}
int ans=;
if(c1()) ans=;
else if(c2()) ans=;
else if(c3()) ans=;
else if(c4()) ans=;
else if(c5()) ans=;
else ans=;
printf("Case %d: %d\n",++o,ans);
}
return ;
} }
signed main(){
Miracle::main();
return ;
} /*
Author: *Miracle*
Date: 2019/2/26 18:48:55
*/