// THIS PROGRAM IS A COMPLETE TIC TAC TOE CLASS

#include <iostream.h>

enum Side { Human, Computer, Empty };
enum PositionVal { HumanWin, Draw, Unclear, ComputerWin };

class TicTacToe
{
  public:
    TicTacToe( ) { ClearBoard( ); }   // Constructor

        // Find optimal move
    int ChooseMove( Side S, int & BestRow, int & BestColumn );
        // Play move, including checking legality
    int PlayMove( Side S, int Row, int Column );
        // Value of the current position
    int PositionValue( ) const; 
    
        // Simple supporting routines
    void ClearBoard( );
    int GetMove(int & Row, int & Column);  // get player's move
    int BoardIsFull( ) const;
    int IsAWin( Side S ) const;
    void Display();

  private:
    int Board[3][3];

    // Play a move, possible claering a square
    void Place( int Row, int Column, int Piece = Empty )
        { Board[ Row ][ Column ] = Piece; }
    
    int SquareIsEmpty( int Row, int Column ) const
        { return Board[ Row ][ Column ] == Empty; }

};

void TicTacToe::Display() 
{     int i;
      for( i = 0; i < 3; i++ ) {
        for( int j = 0; j < 3; j++ ) {
            switch (Board[ i ][ j ]) {
              case Computer: cout << "C"; break;
              case Human: cout << "H"; break;
              default: cout << " ";
            }
            if (j<2) cout << "|";
        }
        cout << "\n";
        if (i<2) cout << "-----\n";
      }
      cout << "\n\n";
}
    
int
TicTacToe::PlayMove ( Side S, int Row, int Column )
{
  Board[Row][Column] = S;
}

void
TicTacToe::ClearBoard ( )
{
    for( int i = 0; i < 3; i++ )
        for( int j = 0; j < 3; j++ )
            Board[ i ][ j ] = Empty;
}

int 
TicTacToe:: GetMove( int & Row, int & Column ) {
   int Value;
   cout << "Enter row and column (0, 1, 2) of move: ";
   cin >> Row >> Column;
   while (Board[Row][Column] != Empty) {
      cout << "\nPosition occupied, try again: ";
      cin >> Row >> Column;
   }
   cout << "\nThank you!\n\n";
   Place (Row, Column, Human);
   Value = PositionValue();        // evaluate the move
   Place (Row, Column, Empty);
   return Value;
}

int 
TicTacToe::BoardIsFull( ) const {
    int result = 1;
    for( int i = 0; i < 3; i++ )
        for( int j = 0; j < 3; j++ )
           if (Board[i][j]==Empty)
              result = 0;
    return result;
}

int 
TicTacToe::IsAWin( Side S ) const {
    for( int i = 0; i < 3; i++ )
       if (S==Board[i][0] && S==Board[i][1] && S==Board[i][2] ||
           S==Board[0][i] && S==Board[1][i] && S==Board[2][i])
       return 1;
    if (S==Board[0][0] && S==Board[1][1] && S==Board[2][2] ||
        S==Board[0][2] && S==Board[1][1] && S==Board[2][0])
       return 1;
    return 0;
}

int
TicTacToe::PositionValue( ) const
{
    if   ( IsAWin( Computer ) ) return ComputerWin ;
    else if ( IsAWin( Human ) ) return HumanWin ;
    else if ( BoardIsFull( ) )  return Draw ;
    else                        return Unclear;
}

int
TicTacToe::ChooseMove( Side S, int & BestRow, int & BestColumn )
{
    Side Opp;             // The other side
    int Reply;            // Value of opponent's reply
    int Value;            // Value of best move so far
    int Dc;               // Placeholder
    int SimpleEval;       // Result of an immediate evaluation

    if( ( SimpleEval = PositionValue( ) ) != Unclear )
        return SimpleEval;

    if( S == Computer )
    {
        Opp = Human; Value = HumanWin;
    }
    else
    {
        Opp = Computer; Value = ComputerWin;
    }

    for( int Row = 0; Row < 3; Row++ )
        for( int Column = 0; Column < 3; Column++ )
            if( SquareIsEmpty( Row, Column ) )
            {
                Place( Row, Column, S );
                Reply = ChooseMove( Opp, Dc, Dc);
                Place( Row, Column, Empty );
                if( S == Computer && Reply > Value ||
                    S == Human && Reply < Value )
                {
                    Value = Reply;
                    BestRow = Row; BestColumn = Column;
                }
            }
            
    return Value;
}