pku acm 1321 源码

#include <iostream>
using namespace std ;
char a[8][8] ;
bool row[8] , col[8] ;
int n , k ;
int sum ;

void dfs( int x , int y ,int step)
{
int i , j ;
if ( step > k )
{
sum++ ;
return;
}

for ( i = x ; i < n ; i++ )
{
for ( j = 0 ; j < n ; j++ )
{
if ( a[i][j] == '#' && row[i] == 0 && col[j] == 0 )
{
row[i] = 1 ;
col[j] = 1 ;
a[i][j] = '.' ;
dfs(i , j ,step+1) ;
row[i] = 0 ;
col[j] = 0 ;
a[i][j] = '#' ;
}
}
}
}
int main()
{
int i , j ;
while ( true )
{
cin >> n >> k ;
if ( n == -1 && k == -1 )
break ;
memset( row , 0 , sizeof(row) ) ;
memset( col , 0 , sizeof(col) ) ;
for ( i = 0 ; i < n ; i++ )
for ( j = 0 ; j < n ; j++ )
cin >> a[i][j] ;
sum = 0 ;
dfs( 0 , 0 ,1) ;
cout << sum << endl ;
}
return 0 ;
}