poj1321 棋盘问题 dfs

///2014.3.30
///poj1321

#include <iostream>
#include <cstdio>
using namespace std;

int N,K;
bool board[10][10];
bool used[10];
int C;

void init(){
char temp;
for(int i=1 ; i<=N ; i++){
used[i] = false;
for(int j=1 ; j<=N ; j++){
cin>>temp;
if( temp=='#' )
board[i][j] = true;
else
board[i][j] = false;
}
}
C = 0;
}

void dfs(int r,int num){
if( num==K ){
C++;
return;
}
if( r>N )
return;
for(int i=1 ; i<=N ; i++){
if( board[r][i] && !used[i] ){
used[i] = true;
dfs(r+1,num+1);
used[i] = false;
}
}
dfs(r+1,num);
}

int main()
{
// freopen("in","r",stdin);
// freopen("out","w",stdout);

while( cin>>N>>K && N!=-1 && K!=-1 ){
init();
dfs(1,0);
cout<<C<<endl;
}
return 0;
}