Checking the Board

To detect a draw, we need to check if all 9 cells are filled. We can use a loop instead of checking each cell manually.

For Loops:

Loops let you repeat code multiple times.

Syntax:

for (uint i = 0; i < 9; i++) { ... }

This has three parts:

1. Start: uint i = 0 - Create variable i, set it to 0

2. Condition: i < 9 - Keep looping while i is less than 9

3. Increment: i++ - After each loop, add 1 to i

Example:

This loop runs 9 times. i will be 0, then 1, then 2... up to 8.

Create a function called isBoardFull that loops through all 9 cells. If any cell is Empty, return false. If the loop finishes, return true.

Create isBoardFull function

Requirements:

Declares function isBoardFull

Function is public view

Returns bool

Has for loop

Checks if cell is Empty

Returns false if Empty found

Returns true after loop

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract TicTacToe {
    address public playerX;
    address public playerO;

    enum Cell { Empty, X, O }

    Cell[9] public board;

    bool public xTurn;

    function startGame(address _opponent) public {
        playerX = msg.sender;
        playerO = _opponent;
        xTurn = true;
    }

    function makeMove(uint _position) public {
        require(_position < 9, "Invalid position");
        require(board[_position] == Cell.Empty, "Cell already taken");
        require(xTurn ? msg.sender == playerX : msg.sender == playerO, "Not your turn");

        Cell piece = xTurn ? Cell.X : Cell.O;
        board[_position] = piece;

        xTurn = !xTurn;
    }

    // Add isBoardFull function here
}