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Tic-Tac-Toe: Validating whether position has already been taken!

MisterTams (125)
I am trying to make the player have to try to select a position again if a spot has already been occupied previously by Player 1 or Player 2. I am not sure why this little class member function I made will not work. What the program does when it runs is that it allows Player 1 (when you select Player 1 to be (X)) to select the first position, then no matter what Player 2 selects it will keep looping and outputting for the user to try again...

If the vector element locations store anything else (such as X or O) it should return true back to main() and start the validation loop to prompt the user to pick a different spot.

Even if all except for one element location have numbers, it still acts as if these spots are already occupied with an X or O.

The class member function I am referring to is bool Game::CheckPosition()
Please help.

Thanks,
MisterTams

Here is the full .cpp file

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#include <iostream>
#include "Game.h"
using namespace std;

//function prototype
void titleFormatting();
void SetGameColor();
int SetPlayerXorO();
void ClearScreen();

int main()
{
	int PlayerXorO;
	bool GameOver = false;
	bool IsItOccupied;
	int Position;

	//function calls
	titleFormatting();
	SetGameColor();
	titleFormatting();
	PlayerXorO = SetPlayerXorO();

	Game TicTacToe(PlayerXorO); //create NewGame object
	
	if (PlayerXorO == 1)
	{
		while (GameOver != true)
		{
			TicTacToe.ShowGameBoard();
			Position = TicTacToe.Player1Xselection();
			IsItOccupied = TicTacToe.CheckPosition();

			while (IsItOccupied == true)
			{
				cout << "This spot has already been chosen!" << endl;
				cout << "Please try again!" << endl;
				Position = TicTacToe.Player1Xselection();
				IsItOccupied = TicTacToe.CheckPosition();
			}

			TicTacToe.setLocationX();
			GameOver = TicTacToe.CheckForWinner();
			ClearScreen();

			TicTacToe.ShowGameBoard();
			Position = TicTacToe.Player2Oselection();
			IsItOccupied = TicTacToe.CheckPosition();

			while (IsItOccupied == true)
			{
				cout << "This spot has already been chosen!" << endl;
				cout << "Please try again!" << endl;
				Position = TicTacToe.Player2Oselection();
				IsItOccupied = TicTacToe.CheckPosition();
			}

			TicTacToe.setLocationO();
			GameOver = TicTacToe.CheckForWinner();

			ClearScreen();
		}

	}
	else if (PlayerXorO == 2)
		cout << endl;
	
	system("pause");
	return 0;
}

/*
FORMATS THE TITLE SCREEN
*/
void titleFormatting()
{
	const int SIZE = 23;
	char TitleTOP[SIZE];
	char TitleBOTTOM[SIZE];

	for (int x = 0; x < SIZE; x++)
	{
		TitleTOP[x] = '-';
		cout << TitleTOP[x];
	}

	cout << "\n******TIC TAC TOE******" << endl;

	for (int x = 0; x < SIZE; x++)
	{
		TitleBOTTOM[x] = '-';
		cout << TitleBOTTOM[x];
	}

	cout << endl;


}
/*
SETS THE GAME SCREEN BACKGROUND AND FONT COLOR
*/
void SetGameColor()
{
	int ColorChoice;
	cout << "\n1. Black Background, White Text" << endl;
	cout << "2. Light Aqua Background, Black Text" << endl;
	cout << "3. Blue Background, Light Aqua Text\n" << endl;

	cout << "Please set a game color: ";
	cin >> ColorChoice;

	if (ColorChoice == 1)
		cin.ignore();
	else if (ColorChoice == 2)
		system("color B0");
	else if (ColorChoice == 3)
		system("color 1B");

	cin.ignore();

	system("cls");
}

/*
SETS AND RETURNS THE PLAYER CHOICE 
RETURNED VALUE IS USED WITH AN OBJECT TO SET
EACH PLAYERS SYMBOL
*/
int SetPlayerXorO()
{
	int choice;
	cout << "\nPlayer 1" << endl;
	cout << "Please choose (X) or (O)" << endl;
	cout << "\n1. Choice: (X)" << endl;
	cout << "2. Choice: (O)" << endl;
	cout << "\nEnter 1 or 2: " << endl;
	cin >> choice;

	while (choice != 1 && choice != 2)
	{
		cout << "\nInvalid! Enter only 1 or 2!";
		cin.clear();
		cin.ignore();
		cin >> choice;
	}
	
	system("cls");
	return choice;
}

void ClearScreen()
{
	system("cls");
}


/*
Class Member Function that checks to see if the game is finally over
*/
bool Game::CheckForWinner()
{
		if (PrintBoard[0][0] == PrintBoard[0][1] && PrintBoard[0][1] == PrintBoard[0][2])
		{
			if (PrintBoard[0][0] == 'O')
			{
				cout << "\nWinner: O" << endl;
				cout << "Loser: X" << endl;
			}
			else
			{
				cout << "\nWinner: X" << endl;
				cout << "Loser: O" << endl;
			}
			return true;
		}
		else if (PrintBoard[0][0] == PrintBoard[1][1] && PrintBoard[1][1] == PrintBoard[2][2])
		{
			if (PrintBoard[0][0] == 'O')
			{
				cout << "\nWinner: O" << endl;
				cout << "Loser: X" << endl;
			}
			else
			{
				cout << "\nWinner: X" << endl;
				cout << "Loser: O" << endl;
			}
			return true;
		}
		else if (PrintBoard[1][0] == PrintBoard[1][1] && PrintBoard[1][1] == PrintBoard[1][2])
		{
			if (PrintBoard[1][0] == 'O')
			{
				cout << "\nWinner: O" << endl;
				cout << "Loser: X" << endl;
			}
			else
			{
				cout << "\nWinner: X" << endl;
				cout << "Loser: O" << endl;
			}
			return true;
		}
		else if (PrintBoard[2][0] == PrintBoard[2][1] && PrintBoard[2][1] == PrintBoard[2][2])
		{
			if (PrintBoard[2][0] == 'O')
			{
				cout << "\nWinner: O" << endl;
				cout << "Loser: X" << endl;
			}
			else
			{
				cout << "\nWinner: X" << endl;
				cout << "Loser: O" << endl;
			}
			return true;
		}
		else if (PrintBoard[0][2] == PrintBoard[1][1] && PrintBoard[1][1] == PrintBoard[2][0])
		{
			if (PrintBoard[0][2] == 'O')
			{
				cout << "\nWinner: O" << endl;
				cout << "Loser: X" << endl;
			}
			else
			{
				cout << "\nWinner: X" << endl;
				cout << "Loser: O" << endl;
			}
			return true;
		}
		else if (PrintBoard[0][0] == PrintBoard[1][0] && PrintBoard[1][0] == PrintBoard[2][0])
		{
			if (PrintBoard[0][0] == 'O')
			{
				cout << "\nWinner: O" << endl;
				cout << "Loser: X" << endl;
			}
			else
			{
				cout << "\nWinner: X" << endl;
				cout << "Loser: O" << endl;
			}
			return true;
		}
		else if (PrintBoard[0][1] == PrintBoard[1][1] && PrintBoard[1][1] == PrintBoard[2][1])
		{
			if (PrintBoard[0][1] == 'O')
			{
				cout << "\nWinner: O" << endl;
				cout << "Loser: X" << endl;
			}
			else
			{
				cout << "\nWinner: X" << endl;
				cout << "Loser: O" << endl;
			}
			return true;
		}
		else if (PrintBoard[0][2] == PrintBoard[1][2] && PrintBoard[1][2] == PrintBoard[2][2])
		{
			if (PrintBoard[0][2] == 'O')
			{
				cout << "\nWinner: O" << endl;
				cout << "Loser: X" << endl;
			}
			else
			{
				cout << "\nWinner: X" << endl;
				cout << "Loser: O" << endl;
			}
			return true;
		}
		else
		{
			return false;
		}
}

bool Game::CheckPosition()
{
	if (PrintBoard[0][0] != '1')
		return true;
	if (PrintBoard[0][1] != '2')
		return true;
	if (PrintBoard[0][2] != '3')
		return true;
	if (PrintBoard[1][0] != '4')
		return true;
	if (PrintBoard[1][1] != '5')
		return true;
	if (PrintBoard[1][2] != '6')
		return true;
	if (PrintBoard[2][0] != '7')
		return true;
	if (PrintBoard[2][1] != '8')
		return true;
	if (PrintBoard[2][2] != '9')
		return true;

	return false;
}


Last edited on
MisterTams (125)


This is my header file
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#ifndef GAME_H
#define GAME_H
#include <vector>
#include <iostream>
using namespace std;

class Game
{

private:
	int location;
	int TotalPicks;
	char Player1Symbol;
	char Player2Symbol;
	vector <vector<char>> PrintBoard = // provide a default member initialiser (equivalent to 2D Array)
	{
		{ '1', '2', '3' },
		{ '4', '5', '6' },
		{ '7', '8', '9' }
	};

public:
	Game(int PlayerChoice)
	{
		if (PlayerChoice == 1)
		{
			Player1Symbol = 'X';
			Player2Symbol = 'O';
		}
		else if (PlayerChoice == 2)
		{
			Player1Symbol = 'O';
			Player2Symbol = 'X';
		}
		
		TotalPicks = 0;
		location = 0;
	}

	bool CheckForWinner();
	bool CheckPosition();
	
	void ShowGameBoard()
	{
		cout << endl;

		for (int x = 0; x < 3; x++)
		{
			for (int y = 0; y < 3; y++)
			{
				cout << "|" << PrintBoard[x][y];
			}
			cout << "|" << endl;
		}
	}

	int Player1Xselection()
	{
		int location;
		cout << "\nPlayer 1 (X)" << endl;
		cout << "Please choose a location (1-9): " << endl;
		cin >> location;

		while (location < 1 || location > 9)
		{
			cout << "Invalid! Please choose 1-9 only!" << endl;
			cout << "Enter: " << endl;
			cin.clear();
			cin.ignore();
			cin >> location;
		}
		
		this->location = location;
		return location;
	}

	int Player1Oselection()
	{
		int location;
		cout << "\nPlayer 1 (O)" << endl;
		cout << "Please choose a location (1-9): " << endl;
		cin >> location;

		while (location < 1 || location > 9)
		{
			cout << "Invalid! Please choose 1-9 only!" << endl;
			cout << "Enter: " << endl;
			cin.clear();
			cin.ignore();
			cin >> location;
		}

		this->location = location;
		return location;
	}

	int Player2Xselection()
	{
		int location;
		cout << "\nPlayer 2 (X)" << endl;
		cout << "Please choose a location (1-9): " << endl;
		cin >> location;

		while (location < 1 || location > 9)
		{
			cout << "Invalid! Please choose 1-9 only!" << endl;
			cout << "Enter: " << endl;
			cin.clear();
			cin.ignore();
			cin >> location;
		}

		this->location = location;
		return location;
	}

	int Player2Oselection()
	{
		int location;
		cout << "\nPlayer 2 (O)" << endl;
		cout << "Please choose a location (1-9): " << endl;
		cin >> location;

		while (location < 1 || location > 9)
		{
			cout << "Invalid! Please choose 1-9 only!" << endl;
			cout << "Enter: " << endl;
			cin.clear();
			cin.ignore();
			cin >> location;
		}

		this->location = location;
		return location;
	}

	void setLocationX()
	{
		if (Player1Symbol == 'X' || Player2Symbol == 'X')
		{
			if (location == 1)
				PrintBoard[0][0] = 'X';
			else if (location == 2)
				PrintBoard[0][1] = 'X';
			else if (location == 3)
				PrintBoard[0][2] = 'X';
			else if (location == 4)
				PrintBoard[1][0] = 'X';
			else if (location == 5)
				PrintBoard[1][1] = 'X';
			else if (location == 6)
				PrintBoard[1][2] = 'X';
			else if (location == 7)
				PrintBoard[2][0] = 'X';
			else if (location == 8)
				PrintBoard[2][1] = 'X';
			else if (location == 9)
				PrintBoard[2][2] = 'X';
		}

	}

	void setLocationO()
	{
		if (Player1Symbol == 'O' || Player2Symbol == 'O')
		{
			if (location == 1)
				PrintBoard[0][0] = 'O';
			else if (location == 2)
				PrintBoard[0][1] = 'O';
			else if (location == 3)
				PrintBoard[0][2] = 'O';
			else if (location == 4)
				PrintBoard[1][0] = 'O';
			else if (location == 5)
				PrintBoard[1][1] = 'O';
			else if (location == 6)
				PrintBoard[1][2] = 'O';
			else if (location == 7)
				PrintBoard[2][0] = 'O';
			else if (location == 8)
				PrintBoard[2][1] = 'O';
			else if (location == 9)
				PrintBoard[2][2] = 'O';
		}

	}
};

#endif

closed account (48T7M4Gy)
if the game position != '1' then return true.

What happens if it contains '9'??

Why not just initialize the grid to '-' everywhere? The cell is vacant if it contains '-' otherwise it is not vacant?
MisterTams (125)
kemort,

But I am not really interested in doing that.
It is user friendly to just select a number 1 through 9 from a display.

My if statements look good to me. I used the debugger as well. I have no idea why IsItOccupied keeps changing to true regardless of what Player 2 chooses for the first move with (O).
JLBorges (13770)
Something along these lines, perhaps:

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#include <vector>
#include <iostream>

struct Game
{
    const char player_one_symbol = 'X' ;
    const char player_two_symbol = 'O' ;

    std::vector< std::vector<char> > board = // provide a default member initialiser
    {
        {'1', '2', '3'},
        {'4', '5', '6'},
        {'7', '8', '9'}
    };

    char at( int loc ) const // return char at location loc [1,9]
    {
        --loc ; // make zero-based
        return board[loc/3][loc%3] ;
    }

    char& at( int loc ) // return char at location loc [1,9]
    {
        --loc ; // make zero-based
        return board[loc/3][loc%3] ;
    }

    bool available( int loc ) const // return true if 'loc' is available
    { return loc > 0 && loc < 10 && at(loc) == loc + '0' ; }

    bool game_over() const { return /* win detected || */ num_availacle() == 0 ; }

    int num_availacle() const // return count of available locations
    {
        int cnt = 0 ;
        for( int loc = 1 ; loc < 10 ; ++loc ) if( available(loc) ) ++cnt ;
        return cnt ;
    }

    int player_one_selection() { return selection(player_one_symbol) ; }
    int player_two_selection() { return selection(player_two_symbol) ; }

    int selection( char player_symbol )
    {
        std::cout << "Please choose a location (1-9): " ;

        int loc ;
        if( std::cin >> loc && available(loc) )
        {
            at(loc) = player_symbol ;
            return loc ;
        }

        std::cin.clear() ; // clear possible failed state (eg. user may not have entered a number)
        std::cin.ignore( 1000, '\n' ) ; // discard the characters in the input buffer
        std::cout << "invalid location / location is already taken. try again\n" ;
        return selection(player_symbol) ;
    }

    std::ostream& print_board( std::ostream& stm = std::cout ) const
    {
        for( const auto& row : board )
        {
            for( char c : row ) stm << c << ' ' ;
            stm << '\n' ;
        }
        return stm << '\n' ;
    }
};

int main()
{
    Game g ;
    g.print_board() ;

    bool player_one_next = true ;
    while( !g.game_over() ) // testing: no checks for win
    {
        if( player_one_next ) g.player_one_selection() ;
        else g.player_two_selection() ;
        g.print_board() ;
        player_one_next = !player_one_next ; // toggle player
    }
}
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