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Grokking the Coding Interview Patterns in Go

Design Tic-Tac-Toe

Explore how to design a TicTacToe game struct that supports moves and winning conditions on an n by n board. Learn to track game state effectively, handle player moves, and determine the winner through horizontal, vertical, and diagonal checks. This lesson helps you implement game logic critical for coding interviews.

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Statement

Suppose that two players are playing a tic-tac-toe game on an n×nn \times n board. They’re following specific rules to play and win the game:

  • A move is guaranteed to be valid if a mark is placed on an empty block.
  • No more moves are allowed once a winning condition is reached.
  • A player who succeeds in placing nn of their marks in a horizontal, vertical, or diagonal row wins the game.

Implement a TicTacToe struct, which will be used by two players to play the game and win fairly.

Keep in mind the following functionalities that need to be implemented:

  • NewTicTacToe(), initializes an object of TicTacToe, allowing the players to play on a board of size n×nn \times n.
  • move(row, col, player) indicates that the player with the ID, player, places their mark on the cell (row, col). The move is guaranteed to be a valid move. At each move, this function returns the player ID if the current player wins and returns 00 if no one wins.

Constraints:

  • 2≤n≤92 \leq n \leq 9

  • player should be either 1 or 2.

  • 0≤0 \leq row, col <n< n

  • Every call to move() will be with a unique row, col combination.

  • The move() function will be called at most n2n^2 times.

Examples

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Understanding the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps us to check if you’re solving the correct problem:

Design Tic-Tac-Toe

1.

We are given the current state of a game on a 3×33 \times 3 board, showing the moves made so far, where Player 1’s moves are denoted by a cross, and Player 2’s moves are denoted by a circle.

The following moves are now made by the players:

move(0, 2, 2)
move(1, 0, 1)

What would the result be?

A.

Player 1 wins the game.

B.

Player 2 wins the game.

C.

No one wins the game.

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Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Note: This puzzle relates only to the function, move(). The data structures that are set up in the constructor, NewTicTacToe, have been mentioned in the first card.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
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Try it yourself

Implement your solution in the following coding playground.

Go
usercode > tic_tac_toe.go
package main
type TicTacToe struct {
	// Write your code here
}
// Constructor will be used to initialize TicTacToe data members 
func (this *TicTacToe) NewTicTacToe(n int) {
	// Write your code here
}
// move will be used to play a move by a specific player and identify who
// wins at each move
func (this *TicTacToe) move(row int, col int, player int) int {
	// Replace this placeholder return statement with your code
	return -1
}
Design Tic-Tac-Toe