#include<iostream.h>

#include"EightQueens.h"

#include"time.h"

void main()

/*

Pre:  The user enters a valid board size.

Post: All solutions to the n-queens puzzle for the selected

      board size are printed.

Uses: The class Queens and the recursive function solve_from.

*/

{

   int board_size;

   void solve_from(Queens &configuration);

   void print_information();

   print_information();

   cout << "What is the size of the board? " << flush;

   cin  >> board_size;

   double start=time(NULL);

   if (board_size < 0 || board_size > max_board)

      cout << "The number must be between 0 and " << max_board << endl;

   else {

      Queens configuration(board_size); //   Initialize empty configuration.

      solve_from(configuration);  //  Find all solutions extending configuration.

   }

   double end=time(NULL);

   cout<<"It takes time: "<<(end-start)<<"(s)"<<endl;

}



void print_information()

{

	cout<<"This is the Queens game."<<endl;

}



void solve_from(Queens &configuration)

/*

Pre:  The Queens configuration represents a partially completed

      arrangement of nonattacking queens on a chessboard.

Post: All n-queens solutions that extend the given configuration are printed.

      The configuration is restored to its initial state.

Uses: The class Queens and the function solve_from, recursively.

*/

{

   if (configuration.is_solved()) configuration.print();

   else

      for (int col = 0; col < configuration.board_size; col++)

         if (configuration.unguarded(col)) {

            configuration.insert(col);

            solve_from(configuration);   //   Recursively continue to add queens.

            configuration.remove(col);

         }

}