Tic Tac Toe game - Playing against the computer

**LarryM2020** · 11-18-2020

Hi I'm currently doing a project in first year regarding a Tic Tac Toe game. In the code I currently have I have most of it in order but I'm having quite alot of trouble trying to include playing against the computer instead of player 1 vs player 2. I need to implement random numbers and making it that it's me against the computer but I have tried different solutions without success (the function I created for the computer is empty because the previous code wasn't working)

Can someone point out what I should do to fix this? Thanks

Code:

#include <stdio.h>#include <stdlib.h> 




void board_design();
void marking_board(int, char);
int check_winner();


char grid[10] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };


int main()
{
    int player = 1, i, selection;
    int computer = 1;
    char mark;
    
    do
    {
        board_design();
        player = (player % 2) ? 1 : 2;


        printf("Player %d, enter a number: ", player);
        scanf("%d", &selection);


        mark = (player == 1) ? 'X' : 'O';


        computer_picks();


        marking_board(selection, mark);
        i = check_winner();


        player++;
        computer++;


    } while (i == -1);


    board_design();


    if (i == 1)
        printf("Congratulations! YOU ARE THE WINNER! ", --player);
    else
        printf("Game draw");


    return 0;
}


void board_design()
{
    printf("\n\n\tTic Tac Toe Game\n\n");


    printf("Player 1 (X)  -  Computer (O)\n\n\n");




    printf("     |     |     \n");
    printf("  %c  |  %c  |  %c \n", grid[1], grid[2], grid[3]);


    printf("_____|_____|_____\n");
    printf("     |     |     \n");


    printf("  %c  |  %c  |  %c \n", grid[4], grid[5], grid[6]);


    printf("_____|_____|_____\n");
    printf("     |     |     \n");


    printf("  %c  |  %c  |  %c \n", grid[7], grid[8], grid[9]);


    printf("     |     |     \n\n");
}


void computer_picks()




void marking_board(int selection, char mark)
{
    if (selection == 1 && grid[1] == '1')
        grid[1] = mark;


    else if (selection == 2 && grid[2] == '2')
        grid[2] = mark;


    else if (selection == 3 && grid[3] == '3')
        grid[3] = mark;


    else if (selection == 4 && grid[4] == '4')
        grid[4] = mark;


    else if (selection == 5 && grid[5] == '5')
        grid[5] = mark;


    else if (selection == 6 && grid[6] == '6')
        grid[6] = mark;


    else if (selection == 7 && grid[7] == '7')
        grid[7] = mark;


    else if (selection == 8 && grid[8] == '8')
        grid[8] = mark;


    else if (selection == 9 && grid[9] == '9')
        grid[9] = mark;


    else
    {
        printf("Invalid move, please try again ");
    }
}


int check_winner() {
    
    if (grid[1] == grid[2] && grid[2] == grid[3])
        return 1;


    else if (grid[4] == grid[5] && grid[5] == grid[6])                //Checking to see if the winner has an horizontal match
        return 1;


    else if (grid[7] == grid[8] && grid[8] == grid[9])
        return 1;


    else if (grid[1] == grid[4] && grid[4] == grid[7])
        return 1;


    else if (grid[2] == grid[5] && grid[5] == grid[8])                  //Checking to see if winner has vertical match
        return 1;


    else if (grid[3] == grid[6] && grid[6] == grid[9])
        return 1;




    else if (grid[1] == grid[5] && grid[5] == grid[9])                   // Check if winner has diagonal match
        return 1;
   
    else if (grid[3] == grid[5] && grid[5] == grid[7])
        return 1;




    else if (grid[1] != '1' && grid[2] != '2' && grid[3] != '3' && grid[4] != '4' && grid[5] != '5'
        && grid[6] != '6' && grid[7] != '7' && grid[8] != '8' && grid[9] != '9')                 // No match in the game


        return 0;
    else
        return -1;
}

**LarryM2020** · 11-19-2020

Anyone that can help? Just need some guidance regarding this

**laserlight** · 11-19-2020

What you're basically trying to do is to replace the user input with something generated by the computer. So, since the user input consists of a number representing a square selection, you just need computer_picks() to return a number in the same range, then your marking_board function should do the job but with a different mark representing the computer's selection.

**LarryM2020** · 11-20-2020

Originally Posted by laserlight

What you're basically trying to do is to replace the user input with something generated by the computer. So, since the user input consists of a number representing a square selection, you just need computer_picks() to return a number in the same range, then your marking_board function should do the job but with a different mark representing the computer's selection.

Thank you for the reply back. I have tried using randon numbers (rand) to get the computer to pick a number between 1 and 9 but it doesn't seem to be working for me the way I want it too which is totally confusing me how it's meant to be implemented

**laserlight** · 11-20-2020

Try writing out the steps on paper and then "executing" your algorithm on paper.

It looks like you might be getting confused between whether you want this to be a player versus player or player versus computer, so think carefully about that. You also might want to simplify a bit first, e.g., assume that the player goes first and the computer goes second. Remember that you need to determine not only if the player has won, but if the computer has won.

**Structure** · 11-20-2020

random numbers and making it that it's me against the computer

Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int valid = 1, endGame = 0, currentPlayer = 1 ;

#define playerTwoIsComputer 1

#define playerOne 'X'
#define playerTwo 'O'

char selection, grid[10] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };

void draw_title() {
  system( "cls || clear" ) ;
  printf( "\n\tTic Tac Toe Game\n\n");
  if (playerTwoIsComputer) {
    printf(" Player 1 (%c)  -  Computer (%c) ", playerOne, playerTwo);
  } else {
    printf(" Player 1 (%c)  -  Player 2 (%c) ", playerOne, playerTwo);
  }  
  printf( "\n\n\n");
}

void draw_board() {
  draw_title();
  printf("\t     |     |     \n");
  printf("\t  %c  |  %c  |  %c \n", grid[1], grid[2], grid[3]);
  printf("\t_____|_____|_____\n");
  printf("\t     |     |     \n");
  printf("\t  %c  |  %c  |  %c \n", grid[4], grid[5], grid[6]);
  printf("\t_____|_____|_____\n");
  printf("\t     |     |     \n");
  printf("\t  %c  |  %c  |  %c \n", grid[7], grid[8], grid[9]);
  printf("\t     |     |     \n\n\n");
}

int drawPiece(char character,int index) {
  int onBlock = ( index + 48 );
  if ( grid[index] == onBlock ) {
    grid[index] = character;
    return 1;
  } else { 
    return 0; 
  }
}

void ask_menu() {
  printf(" Player %i, enter a number: ", currentPlayer);
  scanf("%i", &selection);
}

void computerPlayerTwo() {
  int hasValid = 0;
  for (int i=1; i<9; i++) {
    if ((grid[i] != playerOne) && (grid[i] != playerTwo)) {
      hasValid = 1;
    }
  }
 if (hasValid) {
  do {
    selection = ((rand() % 8)+1);
    valid = drawPiece( playerTwo, selection );
  } while (!valid);
 } else {
    draw_board();
    printf("Game Over. Tie.");
    exit(0);
 }
}

int check_results() {
 int cPoint = 0, cLog = 0;
  cPoint = 1; if (grid[cPoint] == grid[cPoint+1] && grid[cPoint+1] == grid[cPoint+2]) return 1;
  cPoint = 4; if (grid[cPoint] == grid[cPoint+1] && grid[cPoint+1] == grid[cPoint+2]) return 1;
  cPoint = 7; if (grid[cPoint] == grid[cPoint+1] && grid[cPoint+1] == grid[cPoint+2]) return 1;  
  cPoint = 1; if (grid[cPoint] == grid[cPoint+3] && grid[cPoint+3] == grid[cPoint+6]) return 1;
  cPoint = 2; if (grid[cPoint] == grid[cPoint+3] && grid[cPoint+3] == grid[cPoint+6]) return 1;
  cPoint = 3; if (grid[cPoint] == grid[cPoint+3] && grid[cPoint+3] == grid[cPoint+6]) return 1;
  cPoint = 1; if (grid[cPoint] == grid[cPoint+4] && grid[cPoint+4] == grid[cPoint+8]) return 1;
  cPoint = 3; if (grid[cPoint] == grid[cPoint+2] && grid[cPoint+2] == grid[cPoint+4]) return 1;
 cPoint = 0; return cPoint;
};

int main( int args, char * argv[] ) { srand(time(0));

draw_board(); void game_over();

while (!endGame) {

  if (currentPlayer == 1) {
   ask_menu();
   valid = drawPiece( playerOne, selection );
  } else {
   if (playerTwoIsComputer) {
      computerPlayerTwo();
   } else {
      ask_menu();
      valid = drawPiece( playerTwo, selection );
   }
  } 
  
  if (valid) {
    if (check_results()) { draw_board(); game_over(); };
    currentPlayer++; 
    if (currentPlayer > 2) currentPlayer = 1;
    draw_board();
  } else {
    draw_board();
    printf(" Invalid selection: %i\nTry again ", selection );
  }

};

return 0;
}

void game_over() {
  if (playerTwoIsComputer && currentPlayer == 2) {
    printf("\nGame Over. Computer won. \n" ); 
  } else {           
    printf("\nGame Over. Player %i won. \n", currentPlayer);
  }
  exit(0);        
}

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