Thread: TicTacToe program - Space taken?

Hi everyone, I apologize for making a new thread but for I wanted to specifically ask "how I should go about coding my program if a space is taken?" Originally it wasn't boolean but after looking at some other codes, I decided to change it into a boolean. I'm almost done with this program finally but this is the only issue. I tried thinking about a do/while loop but couldn't quite get it to work.

I was thinking about doing this but x isn't put into a variable.

			do
			{
			System.out.println("Your Turn");		
			System.out.print("Please make a move (0-8): ");
			int x = Integer.parseInt(keybd.readLine());
 
			User(a,x);
			drawBoard(a);
			} while (SpaceTaken(a,x) == true);

Here's my main routine:

import java.io.*;
 
public class Test 
{
 
public static void main(String args[]) throws IOException
{
	BufferedReader keybd = new BufferedReader(new InputStreamReader(System.in));
 
	String name;
 
	System.out.println("Hello! Welcome to a one-player version of Tic-Tac-Toe!");
 
	System.out.print("Please enter your name: ");
	name = keybd.readLine();
 
	int[] a = new int[9];
 
	int nummoves = 0;
 
 
	while(true)
	{
 
		ExampleBoard();
 
		for (int i = 0; i <= 8; i++)
		{	
 
	System.out.println("Your Turn");		
	System.out.print("Please make a move (0-8): ");
	int x = Integer.parseInt(keybd.readLine());
 
	User(a,x);
	drawBoard(a);
	nummoves++;
 
	if (Winner(a) == true)
	{
		System.out.println("Congratulations " + name + "! You win!");
		break;
	}
	else if (nummoves == 9)
	{
		System.out.println("Cat's game!");
		break;
	}
	else
 
	System.out.println();
	System.out.println("Computer's Turn");
 
	AI(a,x);
	drawBoard(a);
	System.out.println();
	nummoves++;
 
	if (Loser(a) == true)
	{
		System.out.println("Sorry " + name + "! You Lose!");
		break;
	}
		}
		break;
	}
}

Sub-routine if the space is taken (only for the user, so far):

public static boolean SpaceTaken(int[] a, int x)
{
	if (x == 0 && a[0] != 0)
	{
		System.out.println("Sorry, space is taken!");
		return true;
	}
 
	else if (x == 1 && a[1] != 0)
	{
		System.out.println("Sorry, space is taken!");
		return true;
	}
 
	else if (x == 2 && a[2] != 0)
	{
		System.out.println("Sorry, space is taken!");
		return true;
	}
 
	else if (x == 3 && a[3] != 0)
	{
		System.out.println("Sorry, space is taken!");
		return true;
	}
	else if (x == 4 && a[4] != 0)
	{
		System.out.println("Sorry, space is taken!");
		return true;
	}
	else if (x == 5 && a[5] != 0)
	{
		System.out.println("Sorry, space is taken!");
		return true;
	}
	else if (x == 6 && a[6] != 0)
	{
		System.out.println("Sorry, space is taken!");
		return true;
	}
	else if (x == 7 && a[7] != 0)
	{
		System.out.println("Sorry, space is taken!");
		return true;
	}
	else if (x == 8 && a[8] != 0)
	{
		System.out.println("Sorry, space is taken!");
		return true;
	}
	else
		return false;
}

Wow, I would strongly recommend changing your spaceTaken method. You can directly put x into the index of a, therefore reducing your code down to one if-else statement.

I'm somewhat confused, what is your question? Are you asking where should you put the spaceTaken call in your main method? It should be in a 1.5 loop (or a do while loop) surrounding where you're asking the user for their next move.

Originally Posted by helloworld922

Wow, I would strongly recommend changing your spaceTaken method. You can directly put x into the index of a, therefore reducing your code down to one if-else statement.

I'm somewhat confused, what is your question? Are you asking where should you put the spaceTaken call in your main method? It should be in a 1.5 loop (or a do while loop) surrounding where you're asking the user for their next move.

Hi helloworld922, thanks for replying. Basically I was just frustrated with how to get my spaceTaken method to work like it should: loop the user input if the spot is taken already. I already knew where to put it but I wasn't quite sure how to code a working method. I tried a do while loop using the code I had already (for testing purposes) but it ended up looping just the user input. This may have been because I placed it in the wrong spot but I'll take what you've said in mind and work on it tomorrow since it's pretty late.

*edit* So I wasn't really sure what you meant by being able to "directly put x into the index of a" but I changed my method to the following.

public static boolean SpaceTaken(int[] a, int i)
{
	if (a[i] != 0)
		{
			System.out.println("Sorry, space is taken!");
			return true;
		}
	else
		{
			return false;
		}
}

Although the code is shorter, it still pretty much does what the other one did before (I guess since I haven't changed much except shortened it).
I also added the do while loops for each of the inputs but I got confused about the true/false statements, so I apologize if they're flip-flopped. Here's the main with the added do whiles:

public static void main(String args[]) throws IOException
{
	BufferedReader keybd = new BufferedReader(new InputStreamReader(System.in));
 
	System.out.println("Hello! Welcome to a one-player version of Tic-Tac-Toe!");
	System.out.print("Please enter your name: ");
	String name = keybd.readLine();
 
	int[] a = new int[9];		// Creates an array to store 'X' and 'O'
 
	int nummoves = 0;			// Initializes the # of turns
 
	while(true)
	{
		ExampleBoard();					// Creates initial board for user to refer to
 
		for (int i = 0; i <= 8; i++)
		{	
			do
			{
			System.out.println("Your Turn");		
			System.out.print("Please make a move (0-8): ");
			int x = Integer.parseInt(keybd.readLine());
 
			User(a,x);
			drawBoard(a);
			} while (SpaceTaken(a,i) == false);
			nummoves++;
 
			if (Winner(a) == true)			// Checks winning conditions
			{
				System.out.println("Congratulations " + name + "! You win!");
				break;
			}
			else if (nummoves == 9)			// Checks for a tie
			{
				System.out.println("Cat's game!");
				break;
			}
			else
			{
				System.out.println();
				System.out.println("Computer's Turn");
 
				do
				{
				AI(a);
				drawBoard(a);
				System.out.println();
				} while (SpaceTaken(a,i) == false);
				nummoves++;
 
				if (Loser(a) == true)			// Checks for losing conditions
				{
					System.out.println("Sorry " + name + "! You Lose!");
					break;
				}
			}
		}
	break;
	}
}

1. Don't use an int array if you're trying to store characters. There's conveniently a character data type.
2. Are you sure you're populating the array a with 'X' and 'O' (or even at all)? Java is case sensitive. Please post the code for User(a,x);. It's difficult to determine what's going on without it. And while you're at it, why don't you just post the whole code in it's entirety? It's really difficult to debug code which calls mysterious black boxes (aka methods with no given code).

Ok, here are a few things:

1. Remember what you did to SpaceTaken? Try to do that with your other methods (i.e. get rid of all those unecessary if/else's. Only 1 pair is needed, 0 if you make some smart assumptions and code design). Note that the code in each of the different methods will be slightly different, but conceptually will be very similar.
2. You're AI and User methods don't set the tile to 'X' or 'O', but rather to 1 or 2. Rather than look up the unicode equivalent of 'X' or 'O', simply change your AI and User methods to directly set a[i] to 'X' or 'O'
3. Your AI method isn't quite right. It only tries 1 guess. Instead, it should keep guessing until it gets a valid position to put something into (hint: use a while loop).
4. I didn't look through your logic in the main method, but try running the code by hand (i.e. get out a pencil and paper). See if you can figure out what it is your code is doing. Is what it's doing what you expect to happen? If not, how could you change it? Something I can see right away is that you have an unnecessary while(true) statement (and the corresponding break statement at the bottom).