int grid_is_valid(char grid[9][9], int pos)
{
int column;
int row;
char nb;
if (pos == 9 * 9)
return (1);
column = pos / 9;
row = pos % 9;
if (grid[column][row] != '.')
return (grid_is_valid(grid, pos + 1));
nb = '1';
while (nb <= '9')
{
if (is_on_row(nb, grid, row) == 0 &&
is_on_column(nb, grid, column) == 0 &&
is_on_block(nb, grid, column, row) == 0)
{
grid[column][row] = nb;
if (grid_is_valid(grid, pos + 1))
return (1);
}
nb++;
}
grid[column][row] = '.';
return (0);
}
int grid_is_valid(int grid[9][9], int case_nb)
{
int line;
int column;
line = case_nb / 9;
column = case_nb % 9;
if (case_nb == 81)
{
return (1);
}
if (grid[line][column] != 0)
{
return (grid_is_valid(grid, case_nb + 1));
}
return (backtrack(grid, case_nb, line, column));
}
int backtrack(int grid[9][9], int case_nb, int line, int column)
{
int value;
value = 1;
while (value <= 9)
{
if (not_in_line(grid, value, line)
&& not_in_column(grid, value, column)
&& not_in_square(grid, value, line, column))
{
grid[line][column] = value;
if (grid_is_valid(grid, case_nb + 1))
{
return (1);
}
}
value++;
}
grid[line][column] = 0;
return (0);
}
