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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.
*/
#define USE_RAND
#include "generator.h"
#include "solver.h"
#include "backtrack.h"
#include "puzzle.h"
#include <assert.h>
using namespace Sudoku;
using namespace BackTrack;
//--- class Sudoku::Generator --------------------------------------------------
/** Constructor */
Generator::Generator(Puzzle& puzzle, unsigned int givens_count,
bool symmetric, unsigned int max_iter) :
Algorithm(*this, max_iter), puzzle(puzzle), symmetric(symmetric)
{
assert(givens_count <= SDIM);
// Search a random Sudoku solution.
for (bool found = false; !found;)
{
sudoku.reset();
Solver solver(sudoku, true);
solver.find_next_solution();
found = solver.solution_is_valid();
}
// If symmetric pos_list contains only the first halve of all positions.
pos_count = SDIM;
free_count = SDIM - givens_count;
free_center = symmetric && pos_count % 2 != 0 && free_count % 2 != 0;
if (symmetric)
pos_count /= 2, free_count /= 2;
// Fill pos_list with positions in random order.
bool list[pos_count];
unsigned int p, i, c;
for (p = 0; p < pos_count; ++p)
list[p] = true;
for (i = 0; i < pos_count; ++i)
{
c = rand(pos_count - i) + 1;
for (p = 0; p < pos_count; ++p)
if (list[p])
if (--c == 0)
break;
assert(p < pos_count);
list[p] = false;
pos_list[i] = p;
}
}
/** Set the element to the first sibling. */
void Generator::set_first_at(unsigned int level)
{
assert(level < free_count);
free_list[level] = 0;
}
/** Set the element to the next sibling. */
void Generator::set_next_at(unsigned int level)
{
assert(level < free_count);
++free_list[level];
}
/** Reset the element. */
void Generator::reset_at(unsigned int level)
{
}
/** Check if the element is set to the last sibling. */
bool Generator::is_last_at(unsigned int level) const
{
assert(level < free_count);
return free_list[level] >= pos_count - 1;
}
/** Check if the element is valid (following elements ignored). */
bool Generator::is_valid_at(int level) const
{
assert(level < int(free_count));
// free_list contains ordered indices to pos_list.
if (level > 0 && free_list[level] <= free_list[level - 1])
return false;
if (level >= 0 && free_list[level] > pos_count - (free_count - level))
return false;
// Fill list with marks for givens.
bool given_marks[SDIM];
int i;
for (i = 0; i < SDIM; ++i)
given_marks[i] = true;
for (i = 0; i <= level; ++i)
{
Pos p = pos_list[free_list[i]];
given_marks[p] = false;
if (symmetric)
given_marks[p.symmetric()] = false;
}
if (free_center)
given_marks[Pos::center()] = false;
// Set givens in puzzle and check if it has only one solution.
puzzle.set_givens(sudoku, given_marks);
Solver solver(puzzle);
solver.find_next_solution();
assert(solver.solution_is_valid());
solver.find_next_solution();
return !solver.solution_is_valid();
}
/** Check if the level is the last possible level. */
bool Generator::is_last_level(int level) const
{
return level >= int(free_count) - 1;
}
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