我把所有的棋盘区域记下来，这一只要搜索这些区域即可。
不过这样貌似还没有直接按行搜索快。失败
#include<iostream>
using namespace std;
char map[10][10];
int f[10][10],n,k,ans,num_chess;
struct type
{
int x,y;
}chess[65];
bool check(int i, int j)//check if it is possible to put it at (i,j)
{
for(int k=1; k<=n; k++)
if(f[i][k]&&k!=j)return false;
for(int k=1; k<=n; k++)
if(f[k][j]&&k!=i)return false;
return true;
}
void dfs(int cnt, int numchess )
{
if(cnt==k){ ans++; return ; }
if(numchess>num_chess)return ;
int x=chess[numchess].x,y=chess[numchess].y;
if(check(x,y))
{
f[x][y]=1;
dfs(cnt+1,numchess+1);
}
f[x][y]=0;
dfs(cnt, numchess+1);
}
int main()
{
while(cin>>n>>k)
{
if(n==-1 && k==-1)break;
memset(map,0,sizeof map);
memset(f,0,sizeof f);
ans=0;
num_chess=0;
for(int i=1; i<=n; i++)
for(int j=1; j<=n; j++)
{
cin>>map[i][j];
if(map[i][j]=='#')
{
num_chess++;
chess[num_chess].x=i; chess[num_chess].y=j;
}
}
dfs(0,1);
cout<<ans<<endl;
}
system("pause");
return 0;
}