碉堡问题

import java.util.Scanner;
/**
 * Created by m1786 on 2017/4/2.
 */
public class 碉堡问题 {
    static char a[][]=new char[4][4];
    static String s[]=new String[4];
    static int iBest=0;
    static int n;
    public static void main(String args[]){
        Scanner sc=new Scanner(System.in);
        while(true){
            n=sc.nextInt();
            if(n==0){
                return ;
            }
            sc.nextLine();
            for(int i=0;ifor(int i=0;ifor(int j=0;j0,0);
            System.out.println(iBest);
        }

    }
    static boolean canPlace(int m,int n){
        for(int i=n-1;i>=0;i--){
            if(a[m][i]=='O')
                return false;
            if(a[m][i]=='X')
                break;
        }
        for(int i=m-1;i>=0;i--){
            if(a[i][n]=='O')
                return false;
            if(a[i][n]=='X')
                break;
        }
        return true;
    }
    static void dfs(int t,int current){

        int x;int y;
       if(t==n*n){
           if(current>iBest){
               iBest=current;
               return;
           }
       }
       else{
            x=t/n;
            y=t%n;
           if(a[x][y]=='.'&&canPlace(x,y)){
               a[x][y]='O';
               dfs(t+1,current+1);
               a[x][y]='.';
           }
           dfs(t+1,current);
       }
    }
}