#ifndef Sudoku_h_
#define Sudoku_h_

#include <vector>
using namespace std;

class Sudoku {
public:
  //  Construct an empty grid that is n^2 x n^2.  E.g. when n=3, the
  //  grid should be 9x9.
  Sudoku( int n );       
  
  //  Copy constructor.  The resulting Sudoku object should have the
  //  same grid size and the same values in the grid.
  Sudoku( Sudoku const& other );

  //  Make an assignment to the Sudoku grid at the given row and
  //  col(umn).  If a number is already stored at the row,col
  //  location, overwrite it.  Do not check to see if the Sudoku
  //  placement rules are violated.  Do nothing if the row or col
  //  value is out of bounds (less than 0 or greater than n^2-1).
  void assign( int row, int col, int number );

  //  The number squared to make the grid, e.g. for a 9x9 grid the
  //  value returned should be 3.
  int n() const;

  //  The number of rows (columns) in the grid.  When n=3, this value
  //  is 9.
  int n_squared() const;

  //  Remove a number from the grid.  If there is no number there yet,
  //  do nothing.   Do nothing if the row or col value is out of bounds.
  void unassign( int row, int col );

  //  Return true if and only if row and col are within the grid
  //  bounds and the grid has a number stored at  row, col.
  bool is_assigned( int row, int col ) const;

  //  Return the number stored at the given row, col position, using
  //  the "number" reference parameter to return the value.  Return
  //  true if and only if the row, col values are within the valid
  //  range AND a number has been assigned to the indicated location.
  bool get_number( int row, int col, int & number ) const;

  //  Return true if and only if the value of row, col are within the
  //  valid range and the number can be correctly placed at the given
  //  row,col position based on the row, column and grid block tests
  //  described in the HW 3 handout.  Ignore numbers already placed at
  //  the given row and col position in making this test (since this
  //  function will be used to eliminate. 
  bool valid_assignment( int row, int col, int number ) const;

  //  Using the reference parameter "numbers", return the possible
  //  numbers, in increasing order, that can be placed in this row,col
  //  position based on testing the row, the col and the grid block.
  //  Ignore any number that might already be placed at the current
  //  row,col position. If row or col are out of bounds then the
  //  numbers vector should be empty.
  void possible_numbers( int row, int col, vector<int> & numbers ) const;

  //  Return true if and only if all values placed in the current grid
  //  pass the row, col and grid block tests.
  bool is_grid_valid() const;
  
public:
  //  Add your other member functions here

private:
  //  Add your member variables here.
};

#endif