bzoj:4762: 最小集合

原题链接：http://www.lydsy.com/JudgeOnline/problem.php?id=4762

mark一下，有空要好好弄懂

#include<cstdio>
#include<algorithm>
using namespace std;
int read_p,read_ca;
inline int read(){
    read_p=0;read_ca=getchar();
    while(read_ca<'0'||read_ca>'9') read_ca=getchar();
    while(read_ca>='0'&&read_ca<='9') read_p=read_p*10+read_ca-48,read_ca=getchar();
    return read_p;
}
const int MOD=1e9+7;
int n,a,mmh[2][1024][1024];
inline void M(int &x){while(x>=MOD)x-=MOD;while(x<0)x+=MOD;}
int main(){
    register int i,j,k;
    n=read();mmh[0][0][0]=1;
    for (i=1;i<=n;i++){
        a=1023-read();
        for (j=0;j<1024;j++)
        for (k=j;;k=(k-1)&j){
            mmh[i&1][j][k]=mmh[i&1^1][j][k];
            if (!k) break;
        }
        
        for (j=0;j<1024;j++)
        for (k=j;;k=(k-1)&j){
            M(mmh[i&1][j|a][k^(k&a)]+=mmh[i&1^1][j][k]);
            M(mmh[i&1][j|a][(k^(k&a))|(a^(j&a))]-=mmh[i&1^1][j][k]);
            if (!k) break;
        }
    }
    printf("%d\n",mmh[n&1][1023][0]);
}