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/*
* Sudoku: A plug-in for the Video Disk Recorder
*
* Copyright (C) 2005-2007, Thomas Günther <tom@toms-cafe.de>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef VDR_SUDOKU_GENERATOR_H
#define VDR_SUDOKU_GENERATOR_H
#include "sudoku.h"
#include "backtrack.h"
#include "puzzle.h"
namespace Sudoku
{
//--- class Sudoku::Generator ------------------------------------------------
/** Implementation of a backtracking algorithm to generate Sudoku puzzles
*
* To generate Sudoku puzzles two nested backtracking algorithms are used.
* First a random Sudoku solution is searched. Then the algorithm tries to
* remove some numbers so that only the requested number of givens remains.
* Each puzzle is checked with the nested solver algorithm if there is only
* one solution.
*
* Example:
*
* \code
* Puzzle puzzle;
* Generator generator(puzzle, 36);
* generator.find_next_solution();
* bool found = generator.solution_is_valid();
* \endcode
*/
class Generator : public BackTrack::Algorithm, public BackTrack::Solution
{
Puzzle& puzzle;
Puzzle sudoku;
unsigned int free_list[SDIM];
unsigned int free_count;
Pos pos_list[SDIM];
unsigned int pos_count;
bool symmetric;
bool free_center;
public:
/** Constructor */
Generator(Puzzle& puzzle, unsigned int givens_count,
bool symmetric = true, unsigned int max_iter = 0);
/** Set the element to the first sibling. */
virtual void set_first_at(unsigned int level);
/** Set the element to the next sibling. */
virtual void set_next_at(unsigned int level);
/** Reset the element. */
virtual void reset_at(unsigned int level);
/** Check if the element is set to the last sibling. */
virtual bool is_last_at(unsigned int level) const;
/** Check if the element is valid (following elements ignored). */
virtual bool is_valid_at(int level) const;
/** Check if the level is the last possible level. */
virtual bool is_last_level(int level) const;
};
} // namespace Sudoku
#endif // VDR_SUDOKU_GENERATOR_H
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