tic-tac-toe.cpp

#include<bits/stdc++.h>
using namespace std;
  
#define COMPUTER 1
#define HUMAN 2
  
#define SIDE 3 // Length of the board
  
// Computer will move with 'O'
// and human with 'X'
#define COMPUTERMOVE 'O'
#define HUMANMOVE 'X'
  
// A 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;
}
  
// A 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;
}
  
  
// A 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;
}
  
// A function to declare the winner of the game
void declareWinner(int whoseTurn)
{
    if (whoseTurn == COMPUTER)
        printf("COMPUTER has won\n");
    else
        printf("HUMAN has won\n");
    return;
}
  
// A 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);
}
  
// A 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);
}
  
// A 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);
}
  
// A 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) );
}
  
// A function to play Tic-Tac-Toe
void playTicTacToe(int 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 the instructions before playing
    showInstructions();
      
    int moveIndex = 0, x, y;
      
    // Keep playing till the game is over or it is a draw
    while (gameOver(board) == false && 
            moveIndex != SIDE*SIDE)
    {
        if (whoseTurn == COMPUTER)
        {
            x = moves[moveIndex] / SIDE;
            y = moves[moveIndex] % SIDE;
            board[x][y] = COMPUTERMOVE;
            printf("COMPUTER has put a %c in cell %d\n",
                    COMPUTERMOVE, moves[moveIndex]+1);
            showBoard(board);
            moveIndex ++;
            whoseTurn = HUMAN;
        }
          
        else if (whoseTurn == HUMAN)
        {
            x = moves[moveIndex] / SIDE;
            y = moves[moveIndex] % SIDE;
            board[x][y] = HUMANMOVE;
            printf ("HUMAN has put a %c in cell %d\n",
                    HUMANMOVE, moves[moveIndex]+1);
            showBoard(board);
            moveIndex ++;
            whoseTurn = COMPUTER;
        }
    }
  
    // 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 == COMPUTER)
            whoseTurn = HUMAN;
        else if (whoseTurn == HUMAN)
            whoseTurn = COMPUTER;
          
        // Declare the winner
        declareWinner(whoseTurn);
    }
    return;
}
  
// Driver program
int main()
{
    // Let us play the game with COMPUTER starting first
    playTicTacToe(COMPUTER);
      
    return (0);
}