Thread: Tic-tac-toe implementation problems

Here is my problem I'm supposed to write a tic-tac-toe game.By the way this is the biggest program I've ever attempted to write. When I started writing the game I thought that it wouldn't be too difficult to do-boy was I wrong. The specs for the game are that a human plays the computer (random number generator). The human player chooses to be X or O,X moves first. Right now all the game does is prompt the user to choose X or O. After that is done I can play as X or O only. I can fill the game board with X's or O's (run the code thus far to see what I'm talking about). This is what I need to add to the game.

• A way to store a previous move choice and not allow a move to be over written by a subsequent move
• A call to the random number generator to get the computer's move

As for Item one I think that I need to use two arrays to solve this problem:
One is the board[] array that is the actual game board and I think that the other array I need is a copy of the board[] array to store move choices. Lets say I name this array- full[]. The fulll[] array holds the actual move choices. I think that I need to continually search the full array (using a while loop) to find move choices and to prompt the user that they can't pick that spot. For example if the human player chooses number 5 and puts an X in there the computer can not put an O in the same place and the human player cant put another X in space 5. As for problem two I just need to write a function to call a random number generator. Someone point me in the right direction. I don't want anyone to do it for me,but I do need some help. Here is my code to this point:

Code:

#include<stdio.h>

int getXorO(void);
void drawBoard(void);
int human(int x,int board[]);
int computer(int o,int board[]);
int play(int x,char board[]);



int main(void){
    
    int initialChoice;
    char board[9]= {'1','2','3','4','5','6','7','8','9'};
    int humanMove;
    int computerMove;
    
    initialChoice = getXorO();
    drawBoard();
    play(initialChoice,board);
    
    
    
    return 0;
}
int getXorO(void){//player decides to be X or O here and returns the initialChoice to main
    
    
    int initialChoice;
    
    
    printf("Let's play TIC-TAC-TOE!\n\n");
    printf("Do you want to be X or O (X moves first)? ");
    printf("\nEnter 1 for X and 2 for O: ");
   // scanf("%d",&initialChoice);
    
    if(scanf("%i",&initialChoice)!=1){
            printf("\nInvalid input,exiting game \n");
            exit(1);
        }
    
    while(initialChoice!=1 && initialChoice!=2){
        
         printf("Do you want to be X or O (X moves first)? \n");
         printf("Enter 1 for X and 2 for O:");
         if(scanf("%i",&initialChoice)!=1){
             printf("\nInvalid input,exiting game\n");
             exit(1);
         }
          }
    return initialChoice;
    
}//getMove returns initialChoice to be X or O

void drawBoard(void){
    char board[9]= {'1','2','3','4','5','6','7','8','9'};
    
    printf("\n");
    printf("\t %c | %c | %c \n",board[0],board[1],board[2]);
    printf("\t---|---|--- \n");
    printf("\t %c | %c | %c \n",board[3],board[4],board[5]);
    printf("\t---|---|--- \n");
    printf("\t %c | %c | %c \n\n",board[6],board[7],board[8]);
    
    return;
}
int play(int initialChoice,char board[]){
    int i;
    int humanMove;
    int computerMove;
    char X;
    int choice;
    char full[9] = {'1','2','3','4','5','6','7','8','9'};
    
    if(initialChoice==1)
        initialChoice = 88;//ascii for X/set player as X
    else
        initialChoice = 79;//ascii for O/set player as O
        
    printf("Enter the number of an available space you are,%c: ",initialChoice);
                                             
    scanf("%d",&choice);
    
    for(i=0;i<9;i++){
       
        board[choice-1]= 88;
        
        while(board[choice]==88)
            printf("\nError");
    
    
    printf("\n");
    printf("\t %c | %c | %c \n",board[0],board[1],board[2]);
    printf("\t---|---|--- \n");
    printf("\t %c | %c | %c \n",board[3],board[4],board[5]);
    printf("\t---|---|--- \n");
    printf("\t %c | %c | %c \n\n",board[6],board[7],board[8]);
    
    printf("Enter the number of an available space you are,%c: "
                                                  "",initialChoice);
    //should call the computer here
    scanf("%d",&choice);
    }
    
    
    return 0;
}

You can either "remember where you put your move", or basically make a copy of the current board and make the play on this temporary copy.

For the computer to have a decent chance of winning, you probably want to make it a bit clever, and not base it's moves on randomness (because humans will beat it every time in that case).

I wrote a computer strategy not so long ago that was essentially:
1. Try all moves that can be made, and see if it's a win.
2. Block any move that the other player may win from.
3. Take the middle position.
4. Take a corner position (here I do use random numbers to allow the play to be less predictable).
5. Otherwise take a random free point.

I had to actually make it "player friendly" so that it's not always taking a corner in the 4th rule, otherwise I'd never win (either computer wins or it's a draw). I used a formula to use statistics of the win/loose/draw proportions to determine how likely it should be that teh computer would take a corner or not. If the random number was less than the proportion of computer wins + draws, then it would not take a corner. That way, depending on how good the opponent is, it will adjust the difficulty.

--
Mats

Some thoughts:

You should make the "drawBoard" function reusable and either have it affect a global array or pass it an array representing the current state of the board -- "full". You do not need to bother with putting the square numbers in this array, since they are always equal to the element number plus one anyway. Instead, occupy it with three possibilities -- one for free, one for X, and one for O.

If you are sticking to the random move strategy until you get everything working, use to the contents of the "board" or "full" array to form an array of valid choices for computer.

Code:

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

int main() {	      //123456789	
	char board[10]="  x o  x ", full[10];
	int i, n=0, move;
	for (i=0;i<9;i++) {
		if (board[i]==' ') {
			full[n]=i+1;
			n++;
		}
	}
	full[n]='\0';
        printf("Possible choices: ");
	for (i=0;i<strlen(full);i++) printf("&#37;d ",full[i]);
	move=rand() % strlen(full);
	printf("move: %d\n", full[move]);	
}

Unfortunately because of the way rand() works this will always make the same choice, but hopefully the logic is clear.

[edit] sorry, maybe I shouldn't have called the array "full" as it serves a different purpose than yours.

I haven't run your program, but this is usually how TTT works:

Code:

Initialize() all variables.

1) draw the board

Before a move is made, check if the game is already over from the last move. 
IsWin(), IsLose(), or a Cat's game. (total moves from both players can't be greater 
than 9 before the game is over.

If the game is over, announce the winner and give a "Do you want to play again?"
prompt. 
   If so, 
       Initialize() a new game board and reset the variables.
   else
      Goodby() messages

2) If the game is not over, 

        if it's the computers turn to play, 
            find an empty sqr in the board and have the computer make a move 
            (random or otherwise)

        else
             if it's the human's turn to play, give him a prompt to input his move.

3) Check if the move made IsLegal() and IsGood(). 

If it's legal, AND if it's good (it doesn't allow the opponent to win with his 
next move), 
   then let the move, stay put. 

else, 
   undo the move, and return to #2. 
   (note that no board has been drawn yet, so the move was not "really madel", yet.)

Return to #1

You may very well want to use a copy of the game board to undo a move. You do not need to have an array of all possible moves.

You should have logic in IsLegal() saying that
if a sqr is not empty,
no move can be made to that sqr.

For random number generation, just google it: C random number.

Originally Posted by tabstop

Obviously you got a little carried away with the cut and paste there, as they should check the different spots. (That should have been your hint that all you needed to do was

Code:

if (board[choice-1]=='X')

. Also, why don't you check for 'O'?)

I just noticed that and went back and changed the cases. I did get carried away with the cut and paste,but It still does not work properly

Code:

#include<stdio.h>

int getXorO(void);
void drawBoard(void);
int human(int x,int board[]);
int computer(int o,int board[]);
int play(int x,char board[]);



int main(void){
    
    int initialChoice;
    char board[9]= {'1','2','3','4','5','6','7','8','9'};
    int humanMove;
    int computerMove;
    
    initialChoice = getXorO();
    drawBoard();
    play(initialChoice,board);
    
    
    
    return 0;
}
int getXorO(void){//player decides to be X or O here and returns the initialChoice to main
    
    
    int initialChoice;
    
    
    printf("Let's play TIC-TAC-TOE!\n\n");
    printf("Do you want to be X or O (X moves first)? ");
    printf("\nEnter 1 for X and 2 for O: ");
   // scanf("&#37;d",&initialChoice);
    
    if(scanf("%i",&initialChoice)!=1){
            printf("\nInvalid input,exiting game \n");
            exit(1);
        }
    
    while(initialChoice!=1 && initialChoice!=2){
        
         printf("Do you want to be X or O (X moves first)? \n");
         printf("Enter 1 for X and 2 for O:");
         if(scanf("%i",&initialChoice)!=1){
             printf("\nInvalid input,exiting game\n");
             exit(1);
         }
          }
    return initialChoice;
    
}//getMove returns initialChoice to be X or O

void drawBoard(void){
    char board[9]= {'1','2','3','4','5','6','7','8','9'};
    
    printf("\n");
    printf("\t %c | %c | %c \n",board[0],board[1],board[2]);
    printf("\t---|---|--- \n");
    printf("\t %c | %c | %c \n",board[3],board[4],board[5]);
    printf("\t---|---|--- \n");
    printf("\t %c | %c | %c \n\n",board[6],board[7],board[8]);
    
    return;
}
int play(int initialChoice,char board[]){
    int i;
    int humanMove;
    int computerMove;
    int choice;
    char full[9] ={0};
    char X,O;
    
    if(initialChoice==1)
        initialChoice = 88;//ascii for X/set player as X
    else
        initialChoice = 79;//ascii for O/set player as O
        
    printf("Enter the number of an available space you are,%c: ",initialChoice);
                                             
    scanf("%d",&choice);
    
    for(i=0;i<9;i++){
        
        board[choice-1]= 'X';
    
    
    printf("\n");
    printf("\t %c | %c | %c \n",board[0],board[1],board[2]);
    printf("\t---|---|--- \n");
    printf("\t %c | %c | %c \n",board[3],board[4],board[5]);
    printf("\t---|---|--- \n");
    printf("\t %c | %c | %c \n\n",board[6],board[7],board[8]);
    
    printf("Enter the number of an available space you are,%c: "
                                                  "",initialChoice);
    //should call the computer here
    scanf("%d",&choice);
    
    switch(choice-1){
        case 8:if(board[8]=='X');
        printf("That space is taken,choose anohter");
        break;
        case 7: if(board[7]=='X');
        printf("That space is taken,choose another");
        break;
        case 6:if(board[6]=='X');
        printf("That space is taken,choose another");
        break;
        case 5:if(board[5]=='X');
        printf("That space is taken,choose another");
        break;
        case 4:if(board[4]=='X');
        printf("That space is taken,choose another");
        break;
        case 3:if(board[3]=='X');
        printf("That space is taken,choose another");
        break;
        case 2:if(board[2]=='X');
        printf("That space is taken,choose another");
        break;
        case 1:if(board[1]=='X');
        printf("That space is taken,choose another");
        break;
        case 0:if(board[0]=='X');
        printf("That space is taken,choose another");
        break;
                
    }
    
        
    }
    
    return 0;
}