Implementation of Tic-Tac-Toe for 2 person game (User vs. User)

For 1-Person game (User vs. CPU), please refer Implementation of Tic-Tac-Toe game

Rules of the Game

The game is to be played between two people (in this program between HUMAN to HUMAN).
First the game will take the names of the two players as input.
One of the player chooses ‘O’ and the other ‘X’ to mark their respective cells.
There would be a game toss, which will decide which player will move first.
The game starts with one of the players and the game ends when one of the players has one whole row/ column/ diagonal filled with his/her respective character (‘O’ or ‘X’).
If the game is Tie then, A message is displayed “Game is Tie”.

Winning Strategy – An Interesting Fact
If both the players play optimally then it is destined that you will never lose (“although the match can still be drawn”). It doesn’t matter whether you play first or second. In another way – “ Two expert players will always draw ”.
Isn’t this interesting ?

Below is the code for the Game:

C++

// C++ program to play Tic-Tac-Toe 
#include <bits/stdc++.h> 
using namespace std; 
  
// Length of the board 
#define SIDE 3 
  
// Name fo the players 
string PLAYER1, PLAYER2; 
  
// Function to show the current 
// board status 
void showBoard(char board[][SIDE]) 
{ 
    printf("\n\n"); 
  
    printf("\t\t\t %c | %c | %c \n", 
           board[0][0], 
           board[0][1], 
           board[0][2]); 
  
    printf("\t\t\t------------\n"); 
  
    printf("\t\t\t %c | %c | %c \n", 
           board[1][0], 
           board[1][1], 
           board[1][2]); 
  
    printf("\t\t\t------------\n"); 
    printf("\t\t\t %c | %c | %c \n\n", 
           board[2][0], 
           board[2][1], 
           board[2][2]); 
  
    return; 
} 
  
// Function to show the instructions 
void showInstructions() 
{ 
    printf("\t\t\t Tic-Tac-Toe\n\n"); 
  
    printf("Choose a cell numbered "
           "from 1 to 9 as below"
           " and play\n\n"); 
  
    printf("\t\t\t 1 | 2 | 3 \n"); 
    printf("\t\t\t------------\n"); 
    printf("\t\t\t 4 | 5 | 6 \n"); 
    printf("\t\t\t------------\n"); 
    printf("\t\t\t 7 | 8 | 9 \n\n"); 
  
    printf("-\t-\t-\t-\t-\t"
           "-\t-\t-\t-\t-\n\n"); 
  
    return; 
} 
  
// Function to initialise the game 
void initialise(char board[][SIDE], 
                int moves[]) 
{ 
    // Initiate the random number 
    // generator so that the same 
    // configuration doesn't arises 
    srand(time(NULL)); 
  
    // Initially the board is empty 
    for (int i = 0; i < SIDE; i++) { 
        for (int j = 0; j < SIDE; j++) 
            board[i][j] = ' '; 
    } 
  
    // Fill the moves with numbers 
    for (int i = 0; i < SIDE * SIDE; i++) 
        moves[i] = i; 
  
    // randomise the moves 
    random_shuffle(moves, 
                   moves + SIDE * SIDE); 
  
    return; 
} 
  
// Function to declare winner of the game 
void declareWinner(string whoseTurn) 
{ 
    if (whoseTurn == PLAYER1) 
        cout << PLAYER1 << " has won\n"; 
    else
        cout << PLAYER1 << " has won\n"; 
    return; 
} 
  
// Function that returns true if 
// any of the row is crossed with 
// the same player's move 
bool rowCrossed(char board[][SIDE]) 
{ 
    for (int i = 0; i < SIDE; i++) { 
        if (board[i][0] == board[i][1] 
            && board[i][1] == board[i][2] 
            && board[i][0] != ' ') 
            return (true); 
    } 
    return (false); 
} 
  
// Function that returns true if any 
// of the column is crossed with the 
// same player's move 
bool columnCrossed(char board[][SIDE]) 
{ 
    for (int i = 0; i < SIDE; i++) { 
        if (board[0][i] == board[1][i] 
            && board[1][i] == board[2][i] 
            && board[0][i] != ' ') 
            return (true); 
    } 
    return (false); 
} 
  
// Function that returns true if any 
// of the diagonal is crossed with 
// the same player's move 
bool diagonalCrossed(char board[][SIDE]) 
{ 
    if (board[0][0] == board[1][1] 
        && board[1][1] == board[2][2] 
        && board[0][0] != ' ') 
        return (true); 
  
    if (board[0][2] == board[1][1] 
        && board[1][1] == board[2][0] 
        && board[0][2] != ' ') 
        return (true); 
  
    return (false); 
} 
  
// Function that returns true if the 
// game is over else it returns a false 
bool gameOver(char board[][SIDE]) 
{ 
    return (rowCrossed(board) 
            || columnCrossed(board) 
            || diagonalCrossed(board)); 
} 
  
// Function to play Tic-Tac-Toe 
void playTicTacToe(string whoseTurn) 
{ 
    // A 3*3 Tic-Tac-Toe board for playing 
    char board[SIDE][SIDE]; 
  
    int moves[SIDE * SIDE]; 
  
    // Initialise the game 
    initialise(board, moves); 
  
    // Show instructions before playing 
    showInstructions(); 
  
    int moveIndex = 0, x, y; 
    int r, c; 
  
    // Keep playing till the game is 
    // over or it is a draw 
    while (gameOver(board) == false
           && moveIndex != SIDE * SIDE) { 
        if (whoseTurn == PLAYER1) { 
  
        // Lable for player1 worng choice 
        // of row and column 
        player1: 
  
            // Input the desired row and 
            // column by player 1 to 
            // insert X 
            cout << PLAYER1 
                 << " Enter the respective"
                 << " row and column to "
                    "insert X :\n"; 
            cin >> r >> c; 
  
            if (r <= 3 && c <= 3) { 
  
                // To check desired row and 
                // column should be empty 
                if (board[r - 1] == ' ') 
                    board[r - 1] = 'X'; 
  
                // If input is on already 
                // filled position 
                else { 
                    cout << "You cannot Overlap"
                         << " on Already "
                            "filled position:\n"; 
                    goto player1; 
                } 
            } 
  
            // Input is not valid 
            else { 
                cout << "\nInput is not "
                     << "valid please enter "
                     << "right one\n"; 
  
                goto player1; 
            } 
  
            showBoard(board); 
            moveIndex++; 
            whoseTurn = PLAYER2; 
        } 
  
        else if (whoseTurn == PLAYER2) { 
  
        // Lable for player2 worng choice 
        // of row and column 
        player2: 
  
            // Input the desired row and 
            // column by player 1 to 
            // insert X 
            cout << PLAYER2 
                 << " Enter the respective"
                 << " row and column to "
                    "insert O :"; 
            cin >> r >> c; 
            if (r <= 3 && c <= 3) { 
  
                // Input the desired row and 
                // column by player 1 to 
                // insert X 
                if (board[r - 1] == ' ') 
                    board[r - 1] = 'O'; 
  
                // If input is on already 
                // filled position 
                else { 
                    cout << "You cannot Overlap"
                         << " on Already "
                         << "filled position:\n"; 
                    goto player2; 
                } 
            } 
  
            // Input is not valid 
            else { 
                cout << "\nInput is not "
                     << "valid please enter "
                     << "right one :\n"; 
                goto player2; 
            } 
  
            showBoard(board); 
            moveIndex++; 
            whoseTurn = PLAYER1; 
        } 
    } 
  
    // If the game has drawn 
    if (gameOver(board) == false
        && moveIndex == SIDE * SIDE) 
        printf("It's a draw\n"); 
    else { 
  
        // Toggling the user to declare 
        // the actual winner 
        if (whoseTurn == PLAYER1) 
            whoseTurn = PLAYER2; 
        else if (whoseTurn == PLAYER2) 
            whoseTurn = PLAYER1; 
  
        // Declare the winner 
        declareWinner(whoseTurn); 
    } 
    return; 
} 
  
// Driver Code 
int main() 
{ 
    // Take the name of players 
    cout << "Enter name of first Player: "; 
    cin >> PLAYER1; 
  
    cout << "Enter name of Second Player: "; 
    cin >> PLAYER2; 
  
    // Use current time as seed for 
    // random generator 
    srand(time(0)); 
  
    // Lets do toss 
    int toss = rand() % 2; 
  
    // Let us play the game 
    if (toss == 1) { 
        cout << "Player "
             << PLAYER1 
             << " win the toss"
             << endl; 
  
        playTicTacToe(PLAYER1); 
    } 
    else { 
        cout << "Player "
             << PLAYER2 
             << " win the toss"
             << endl; 
        playTicTacToe(PLAYER2); 
    } 
  
    return (0); 
} 

Output:
Below is the output of the above code:

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My Personal Notes

C++

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