POJ - 1321 棋盘问题

#include<iostream>
#include<cstring>
using namespace std;
#define maxn 9
int mmp[maxn][maxn];
bool checky[maxn];
long long n,k,ans;
void dfs(long long x, long long  num){
    if(num==k){
        //cout<<x<<endl;
        ans++;return ;
    }
    for(long long i=x+1;i<=n;i++){
        for(long long j=1;j<=n;j++){
            if(mmp[i][j]&&!checky[j]){
                checky[j]=true;
                dfs(i,num+1);
                checky[j]=false;
            }
        }
    }
}
int main(){
    char get;
    while(cin>>n>>k){
        if(n==-1&&k==-1){
            break;
        }
        ans=0;
        memset(mmp,0,sizeof(mmp));
        memset(checky,0,sizeof(checky));
        for(long long  i=1;i<=n;i++){
            for(long long j=1;j<=n;j++){
                cin>>get;
                if(get=='#') mmp[i][j]=1;
            }
        }
        dfs(0,0);
        cout<<ans<<endl;
    }
    return 0;
}