[Bzoj1083][SCOI2005]互不侵犯king（状压dp）

# include <iostream>
# include <cstdio>
# include <cstring>
using namespace std;
const int N = 1 << 9;
int cnt,state[102],num[102],P,n,c;
long long f[10][102][102];
int lowbit(int r){
    return r & -r;
}
void work(){
    for(int i = 0;i < P;i++){
        int pre = lowbit(i),r = i - pre;bool flag = true;
        while(r){
            if(lowbit(r) / pre <= 2){
                flag = false;break;
            }
            pre = lowbit(r);r -= pre;
        }
        if(flag)state[++cnt] = i;
    }
    for(int i = 1;i <= cnt;i++){
        int r = state[i];
        while(r){
            r -= lowbit(r);
            num[i]++;
        }
    }
}
int main(){
    scanf("%d %d",&n,&c);P = 1 << n;
    work();
    f[0][1][0] = 1LL;
    for(int i = 1;i <= n;i++){
        for(int j = 1;j <= cnt;j++){
            for(int k = 1;k <= cnt;k++){
                for(int l = 0;l <= c;l++){
                if(state[j] & state[k])continue;
                if((state[j] >> 1) & state[k])continue;
                if((state[j] << 1) & state[k])continue;
                f[i][j][l + num[j]] += f[i - 1][k][l];
              }
            }
        }
    }
    long long ans = 0;
    for(int i = 1;i <= cnt;i++){
      ans += f[n][i][c];
    }
    printf("%lld\n",ans);
}