tictactoe.cpp

#include<bits/stdc++.h> 
using namespace std; 
  
#define COMPUTER 1 
#define HUMAN 2 
  
#define SIDE 3 // Length of the board 

#define COMPUTERMOVE 'O' 
#define HUMANMOVE 'X' 
  

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; 
} 
  

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; 
} 
  

void initialise(char board[][SIDE], int moves[]) 
{ 
   
    srand(time(NULL));  
      
    for (int i=0; i<SIDE; i++) 
    { 
        for (int j=0; j<SIDE; j++) 
            board[i][j] = ' '; 
    } 
      
    
    for (int i=0; i<SIDE*SIDE; i++) 
        moves[i] = i; 
  
    random_shuffle(moves, moves + SIDE*SIDE); 
      
    return; 
} 
  
 
void declareWinner(int whoseTurn) 
{ 
    if (whoseTurn == COMPUTER) 
        printf("COMPUTER has won\n"); 
    else
        printf("HUMAN has won\n"); 
    return; 
} 
  

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); 
} 
  
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); 
} 
  
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); 
} 
  

bool gameOver(char board[][SIDE]) 
{ 
    return(rowCrossed(board) || columnCrossed(board) 
            || diagonalCrossed(board) ); 
} 
  

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; 
} 
  

int main() 
{ 
    // Let us play the game with COMPUTER starting first 
    playTicTacToe(COMPUTER); 
      
    return (0); 
}