Tic Tac Toe - Part 2

If you made it to part 2, then you were able to achieve this output:

The next step is to let the players take turns on the board:

Inside the workbook, Scanner was declared as a class variable. That's because you'll need to access Scanner from more than one place inside the class.

public class TicTacToe {

       Scanner scan = new Scanner(System.in);

       public static void main(String[] args) {
          //...
       }

Task 3: Taking turns

The maximum number of turns is 9. Set up a for loop that runs 9 times and prints the counter.

Each run represents a turn, such that X goes first.

Hint: X plays when the counter is even, whereas O plays when the counter is odd. Set up a condition that alternates between printing Turn: X and Turn: O.

Task 4: Write a function

Write a function that asks the user to choose a spot. As you write the function, call it for each turn.

if (X turn) {
    Task 4: call askUser(board).
} else {
    Task 4: call askUser(board).
}

1. Function name: The name of the function is askUser(). It lets the player choose a spot on the board.

/**
 * Function name -- askUser <-------
 * @param board (char[][] board)
 * @return spot (int[])
 *
 * Inside the function
 *     1. Asks the user: - pick the row and column:
 *     2. If the spot is taken, ask the user to choose again.
 *     3. Return the row and column in an int[] array.
 *
 */

2. Parameters: The function takes one parameter: char[][] board.

/**
 * Function name -- askUser
 * @param board (char[][] board) <--------
 * @return spot (int[])
 *
 * Inside the function
 *  1. Asks the user: - pick the row and column:
 *  2. If the spot is taken, ask the user to choose again.
 *  3. Return the row and column in an int[] array.
 *
 */

3. Return value: The function returns the spot. It will be an array that holds two numbers: the row and column.

/**
 * Function name -- askUser
 * @param board (char[][] board)
 * @return spot (int[]) <-------
 *
 * Inside the function
 *  1. Asks the user: - pick the row and column:
 *  2. If the spot is taken, ask the user to choose again.
 *  3. Return the row and column in an int[] array.
 *
 */

Inside the function:

• Ask the player to pick a spot on the grid and return it

/**
 * Function name -- askUser
 * @param board (char[][] board)
 * @return spot (int[])
 *
 * Inside the function <---
 *  1. Asks the user: - pick a row and column number: <---
 *  2. If the spot is taken, ask the user to choose again.
 *  3. Return the row and column in an int[] array. <---
 *
 */

The user will write their numbers beside each question. Then, store both numbers in the int[] array.

Ignore the second step for now. You can move on to task 5.

/**
 * Function name -- askUser
 * @param board (char[][] board)
 * @return spot (int[])
 *
 * Inside the function
 *  1. Asks the user: - pick a row and column number:
 *
 *     *****  Ignore this step for now *****
 *  2. If the spot is taken, ask the user to choose again.
 *     *****  Ignore this step for now *****

 *  3. Return the row and column in an int[] array.
 *
 */

Task 5: Populate the board

---

The function call returns the player's spot. Use that return value to index the board and populate it. Then, print the board:

Task 4: Revisited

---

We can't let the player pick a spot that's already taken.

Inside the function:

• Check if the spot on the board is taken. If so, prompt the user to choose again.

/**
 * Function name -- askUser
 * @param board (char[][] board)
 * @return spot (int[])
 *
 * Inside the function <------
 *  1. Asks the user: - pick a row and column number:
 *  2. If the spot is taken, ask the user to choose again. <----
 *  3. Return the row and column in an int[] array. 
 *
 */

Hint: use a while loop! Final output:

The player tried to pick a spot that was already taken (0 0). The game prompted them to pick another spot.

Good Luck!