[WF2012]infiltration

[WF2012]infiltration

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=0;bool fl=false;
    while(!isdigit(ch=getchar()))(ch=='-')&&(fl=true);
    for(x=numb;isdigit(ch=getchar());x=x*10+numb);
    (fl==true)&&(x=-x);
}
namespace Miracle{
const int N=80;
int n;
char con[N][N];
bitset<N>to[N],now;
bool c1(){
    for(reg a1=1;a1<=n;++a1)
        if(to[a1].count()==n) return true;
    return false;
}
bool c2(){
    for(reg a1=1;a1<=n;++a1)
    for(reg a2=a1+1;a2<=n;++a2)
        if((to[a1]|to[a2]).count()==n) return true;
    return false;
}
bool c3(){
    for(reg a1=1;a1<=n;++a1)
    for(reg a2=a1+1;a2<=n;++a2)
    for(reg a3=a2+1;a3<=n;++a3)
        if((to[a1]|to[a2]|to[a3]).count()==n) return true;
    return false;
}
bool c4(){
    for(reg a1=1;a1<=n;++a1)
    for(reg a2=a1+1;a2<=n;++a2)
    for(reg a3=a2+1;a3<=n;++a3)
    for(reg a4=a3+1;a4<=n;++a4)
        if((to[a1]|to[a2]|to[a3]|to[a4]).count()==n) return true;
    return false;
}
bool c5(){
    for(reg a1=1;a1<=n;++a1)
    for(reg a2=a1+1;a2<=n;++a2)
    for(reg a3=a2+1;a3<=n;++a3)
    for(reg a4=a3+1;a4<=n;++a4)
    for(reg a5=a4+1;a5<=n;++a5)
        if((to[a1]|to[a2]|to[a3]|to[a4]|to[a5]).count()==n) return true;
    return false;
}
int main(){
    int o=0;
    while(scanf("%d",&n)!=EOF){
        for(reg i=1;i<=n;++i) to[i].reset();
        for(reg i=1;i<=n;++i){ 
            scanf("%s",con[i]+1);
            for(reg j=1;j<=n;++j){
                if(i==j) continue;
                if(con[i][j]=='1')to[i][j]=1;
                else to[i][j]=0;
            }
            to[i][i]=1;
        }
        int ans=0;
        if(c1()) ans=1;
        else if(c2()) ans=2;
        else if(c3()) ans=3;
        else if(c4()) ans=4;
        else if(c5()) ans=5;
        else ans=6;
        printf("Case %d: %d
",++o,ans);
    }
    return 0;
}
 
}
signed main(){
    Miracle::main();
    return 0;
}
 
/*
   Author: *Miracle*
   Date: 2019/2/26 18:48:55
*/