UVa639 - Don't Get Rooked

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#include <iostream>
#include <string>
#include <cstring>
using namespace std;
int n;
string board[4];
int max_num;
int visited[4][4];
bool isSafe()
{
	for(int i=0;i<n;++i)
	{
		for(int j=0;j<n;++j)
		{
			if(board[i][j]=='.'&&visited[i][j]==1)
			{
				int a,b;
				a=i-1;b=j;
				while(a>=0&&board[a][b]!='X')
				{
					if(board[a][b]=='.'&&visited[a][b]==1)
						return false;
					--a;
				}
				a=i+1;b=j;
				while(a<n&&board[a][b]!='X')
				{
					if(board[a][b]=='.'&&visited[a][b]==1)
						return false;
					++a;
				}
				a=i;b=j-1;
				while(b>=0&&board[a][b]!='X')
				{
					if(board[a][b]=='.'&&visited[a][b]==1)
						return false;
					--b;
				}
				a=i;b=j+1;
				while(b<n&&board[a][b]!='X')
				{
					if(board[a][b]=='.'&&visited[a][b]==1)
						return false;
					++b;
				}
			}
		}
	}
	return true;
}
void judge(int val)
{
	int num=0;
	memset(visited,0,sizeof(visited));
	for(int i=0;i<n*n;++i)
	{
		
		if(val&(1<<i))
		{
			int a=i/n;
			int b=i%n;
			if(board[a][b]=='X')
				return ;
			++num;
			visited[a][b]=1;
		}
	}
	if(isSafe()&&num>max_num)
		max_num=num;
}
int main()
{
	while(cin>>n&&n!=0)
	{
		for(int i=0;i<n;++i)
			cin>>board[i];
		max_num=-1;
		for(int i=0;i<(1<<(n*n));++i)
			judge(i);
		cout<<max_num<<endl;
	}
	return 0;
}