poj 1321 棋盘问题

#include <map>
#include <set>
#include <queue>
#include <stack>
#include <vector>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int N = 10;

int n, k;
int ans, now;

char a

;
int vis
;

void dfs( int l )
{
	if( now == k )
	{
		ans++;
		return;
	}
	if( l > n )
		return;
	for( int i = 1; i <= n; i++ )
	{
		if( !vis[i] && a[l][i] == '#' )
		{
			vis[i] = 1;
			now++;
			dfs( l+1 );
			now--;
			vis[i] = 0;
		}
	}
	dfs( l+1 );
}

int main()
{
	while(~scanf("%d%d", &n, &k) && (n != -1 && k != -1 ))
	{
		for( int i = 1; i <= n; i++ )
			scanf("%s", a[i]+1);
		memset( vis, 0, sizeof( vis ));
		ans = 0;
		now = 0;
		dfs(1);
		printf("%d\n", ans);
	}
	return 0;
}