bzoj1080

传送门:http://www.lydsy.com/JudgeOnline/problem.php?id=1080
神暴力,待搞懂.
代码

#include <cstdio> 
#include <cmath> 
#include <iostream> 
#include <cstring> 
#include <algorithm> 
#include <vector> 
#include <map> 
#include <queue> 
#define ll long long 
using namespace std; 
typedef vector<int> ve; 
map <ve,int> hash; 
queue<ve>q; 
string s[35]; 
int n; 
void work() 
{ 
    ve u,v,t; 
    for (int i=1;i<=n;i++) 
        if (s[i]=="")  
        { 
            printf("0"); 
            exit(0); 
        } 
        else u.push_back(i<<6); 
    hash[u]=0; 
    for(q.push(u);!q.empty();) 
    { 
        u=q.front(); 
        q.pop(); 
        int x=hash[u],cnt; 
        for (int ch='0';ch<='1';ch++) 
        { 
            cnt=0; 
            v.clear(); 
            for (int i=0;i<u.size();i++) 
            { 
                int which=u[i]>>6,where=u[i]&63; 
                if (s[which][where]^ch) continue; 
                if(++where==s[which].size()) { 
                    ++cnt; 
                for (int j=1;j<=n;j++)v.push_back(j << 6); 
                }else v.push_back(which<<6|where); 
            } 
            if(cnt>=3) 
            { 
                printf("%d",x+1); 
                exit(0); 
            } 
            sort(v.begin(),v.end()); 
            t.clear(); 
            for (int i=0;i<v.size();i++) 
            { 
                if(i<3||v[i]^v[i-3]) t.push_back(v[i]); 
            } 
            int &th=hash[t]; 
            if (t.size()&&!th) th=x+1,q.push(t); 
        } 
    } 
    printf("-1"); 
} 
int main() 
{ 
    scanf("%d",&n); 
    for (int i=1;i<=n;i++) cin>>s[i]; 
    work(); 
    return 0; 
}