Tic-Tac-Toe Game in C++

In this article, we will learn how to develop a tic-tac-toe game in C++. Tic-tac-toe is a game played between two players usually with paper and pencil but here, we will create a C++ program that will display the game on the console screen and players can use different keys from the keyboard to play it.

Before we start, let’s understand some rules to play the game:

Rules of Tic-Tac-Toe

Following are the rules that define how to play the tic tac toe game:

• A player can put only a single letter X or O in the 3 x 3 grid in each chance.
• Both players will get chances alternatively one after another till someone wins or draws. 
• To win this game, the player must create a horizontal, vertical, or diagonal line consisting of three same letters.
• The game is drawn, if all grids are filled with X or O letters but no line is made.

Feature of Tic-Tac-Toe in C++

This game provides the following features:

• This game is developed on a 3×3 grid.
• This game is designed for two players.
• Every player may choose a letter between X and O.
• Both players will get their chances to turn by turn.

Components of the Game

The game is made of the following components that include the functions and data structures to provide the basic operations of the game.

1. Game Board

To create a tic-tac-toe board, a 3 x 3 array initialized with space is used.

char board[3][3] = {{' ', ' ', ' '}, {' ', ' ', ' '}, {' ', ' ', ' '}};

In this array, we will fill the X and O characters based on the moves of the players.

2. Movement Of Player

Now we will create a function drawBoard() to display the Board. It will initialize the array and display the board after each move.

The logic for user input and valid input checking is defined inside the main() function itself.

How to check if the input is valid or not?

• Valid input: If the cell is empty and is within the boundary
• Invalid input: If the cell has already been filled with another letter or is outside the bounds.

3. Win, Lose or Draw

The checkWin() function is used to check whether the player has won or not. The draw condition is checked in the main() function.

C++ Program for Tic Tac Toe Game

Below is the complete code for a basic console-based Tic-Tac-Toe game in C++:

C++

// C++ program to implement tic tac toe game
#include <iostream>
using namespace std;

// Function to draw the Tic-Tac-Toe board
void drawBoard(char board[3][3])
{
    cout << "-------------\n";
    for (int i = 0; i < 3; i++) {
        cout << "| ";
        for (int j = 0; j < 3; j++) {
            cout << board[i][j] << " | ";
        }
        cout << "\n-------------\n";
    }
}

// Function to check for a win
bool checkWin(char board[3][3], char player)
{
    // Check rows, columns, and diagonals
    for (int i = 0; i < 3; i++) {
        if (board[i][0] == player && board[i][1] == player
            && board[i][2] == player)
            return true;
        if (board[0][i] == player && board[1][i] == player
            && board[2][i] == player)
            return true;
    }
    if (board[0][0] == player && board[1][1] == player
        && board[2][2] == player)
        return true;
    if (board[0][2] == player && board[1][1] == player
        && board[2][0] == player)
        return true;
    return false;
}

int main()
{
    // Initialize the board and players
    char board[3][3] = { { ' ', ' ', ' ' },
                         { ' ', ' ', ' ' },
                         { ' ', ' ', ' ' } };
    char player = 'X';
    int row, col;
    int turn; // Declare turn here

    cout << "Welcome to Tic-Tac-Toe!\n";

    // Game loop
    for (turn = 0; turn < 9; turn++) {
        // Draw the board
        drawBoard(board);

        // Prompt for valid input
        while (true) {
            cout << "Player " << player
                 << ", enter row (0-2) and column (0-2): ";
            cin >> row >> col;

            if (board[row][col] != ' ' || row < 0 || row > 2
                || col < 0 || col > 2) {
                cout << "Invalid move. Try again.\n";
            }
            else {
                break; // Valid input, exit the loop.
            }
        }

        // Make the move
        board[row][col] = player;

        // Check for a win after making a move
        if (checkWin(board, player)) {
            drawBoard(board);
            cout << "Player " << player << " wins!\n";
            break; // Exit the loop after a win.
        }

        // Switch to the other player
        player = (player == 'X') ? 'O' : 'X';
    }

    // End of the game
    drawBoard(board);

    // Check for a draw
    if (turn == 9 && !checkWin(board, 'X')
        && !checkWin(board, 'O')) {
        cout << "It's a draw!\n";
    }

    return 0;
}

Output

Welcome to Tic-Tac-Toe!
-------------
|   |   |   | 
-------------
|   |   |   | 
-------------
|   |   |   | 
-------------
Player X, enter row (0-2) and column (0-2): 1 1
-------------
|   |   |   | 
-------------
|   | X |   | 
-------------
|   |   |   | 
-------------
Player O, enter row (0-2) and column (0-2): 0 0
-------------
| O |   |   | 
-------------
|   | X |   | 
-------------
|   |   |   | 
-------------
Player X, enter row (0-2) and column (0-2): 1 0
-------------
| O |   |   | 
-------------
| X | X |   | 
-------------
|   |   |   | 
-------------
Player O, enter row (0-2) and column (0-2): 2 2
-------------
| O |   |   | 
-------------
| X | X |   | 
-------------
|   |   | O | 
-------------
Player X, enter row (0-2) and column (0-2): 1 2
-------------
| O |   |   | 
-------------
| X | X | X | 
-------------
|   |   | O | 
-------------
Player X wins!
-------------
| O |   |   | 
-------------
| X | X | X | 
-------------
|   |   | O | 
-------------