Overview
Let’s first understand what is Tic Tac Toe with an example
- There is an n*n board and each block in the board can be marked with either a cross or a circle only if the block is empty
- Max two players play the game at a time with each taking turn.
- The first player marks a cross at any block in the board in its turn. While the second player marks a circle at any block in the board in its turn.
- The objective is to have either an entire row or an entire column or an entire diagonal with any of the one symbol either cross or circle.
- Both players will try to stop the other player from achieving this objective. Whosoever achieves it first will win.
- If all blocks in the board are full and none of the players have not been able to mark the entire row, column, or diagonal with its symbol then the game results in a draw.
- No more moves are allowed after one player wins the game.
Let’s understand this game with an example. Assume a 3*3 grid. Dot (‘.’) represents an empty block
Player 1 Move with Symbol * at Position X:1 Y:1
...
.*.
...
Player 2 Move with Symbol o at Position X:1 Y:2
...
.*o
...
Player 1 Move with Symbol * at Position X:2 Y:0
...
.*o
*..
Player 2 Move with Symbol o at Position X:0 Y:2
..o
.*o
*..
Player 1 Move with Symbol * at Position X:2 Y:2
..o
.*o
*.*
Player 2 Move with Symbol o at Position X:0 Y:0
o.o
.*o
*.*
Player 1 Move with Symbol * at Position X:2 Y:1
o.o
.*o
***
First Player Win
o.o
.*o
***In the above game First Player Win because the third row is all occupied with symbol cross – ‘*’
Program
Here is the full working code
symbol.go
package main
type Symbol uint8
const (
Cross Symbol = iota
Circle
Dot
)iPlayer.go
package main
type iPlayer interface {
getSymbol() Symbol
getNextMove() (int, int, error)
getID() int
}humanPlayer.go
package main
import "fmt"
var (
MovesPlayer1 = [4][2]int{{1, 1}, {2, 0}, {2, 2}, {2, 1}}
MovesPlayer2 = [4][2]int{{1, 2}, {0, 2}, {0, 0}, {0, 0}}
)
type humanPlayer struct {
symbol Symbol
index int
id int
}
func (h *humanPlayer) getSymbol() Symbol {
return h.symbol
}
func (h *humanPlayer) getNextMove() (int, int, error) {
if h.symbol == Cross {
h.index = h.index + 1
return MovesPlayer1[h.index-1][0], MovesPlayer1[h.index-1][1], nil
} else if h.symbol == Circle {
h.index = h.index + 1
return MovesPlayer2[h.index-1][0], MovesPlayer2[h.index-1][1], nil
}
return 0, 0, fmt.Errorf("Invalid Symbol")
}
func (h *humanPlayer) getID() int {
return h.id
}computerPlayer.go
package main
type computerPlayer struct {
symbol Symbol
id int
}
func (c *computerPlayer) getSymbol() Symbol {
return c.symbol
}
func (c *computerPlayer) getNextMove() (int, int, error) {
//To be implemented
return 0, 0, nil
}
func (c *computerPlayer) getID() int {
return c.id
}gameStatus.go
package main
type GameStatus uint8
const (
GameInProgress GameStatus = iota
GameDraw
FirstPlayerWin
SecondPlayerWin
)board.go
package main
import "fmt"
type board struct {
square [][]Symbol
dimension int
}
func (b *board) printBoard() {
for i := 0; i < b.dimension; i++ {
for j := 0; j < b.dimension; j++ {
if b.square[i][j] == Dot {
fmt.Print(".")
} else if b.square[i][j] == Cross {
fmt.Print("*")
} else {
fmt.Print("o")
}
}
fmt.Println("")
}
}
func (b *board) markSymbol(i, j int, symbol Symbol) (bool, Symbol, error) {
if i > b.dimension || j > b.dimension {
return false, Dot, fmt.Errorf("index input is greater than dimension")
}
if b.square[i][j] != Dot {
return false, Dot, fmt.Errorf("input square already marked")
}
if symbol != Cross && symbol != Circle {
return false, Dot, fmt.Errorf("incorrect Symbol")
}
b.square[i][j] = symbol
win := b.checkWin(i, j, symbol)
return win, symbol, nil
}
func (b *board) checkWin(i, j int, symbol Symbol) bool {
//Check Row
rowMatch := true
for k := 0; k < b.dimension; k++ {
if b.square[i][k] != symbol {
rowMatch = false
}
}
if rowMatch {
return rowMatch
}
//Check Row
columnMatch := true
for k := 0; k < b.dimension; k++ {
if b.square[k][j] != symbol {
columnMatch = false
}
}
if columnMatch {
return columnMatch
}
//Check diagonal
diagonalMatch := false
if i == j {
diagonalMatch = true
for k := 0; k < b.dimension; k++ {
if b.square[k][k] != symbol {
diagonalMatch = false
}
}
}
return diagonalMatch
}game.go
package main
import "fmt"
type game struct {
board *board
firstPlayer iPlayer
secondPlayer iPlayer
firstPlayerTurn bool
moveIndex int
gameStatus GameStatus
}
func initGame(b *board, p1, p2 iPlayer) *game {
game := &game{
board: b,
firstPlayer: p1,
secondPlayer: p2,
firstPlayerTurn: true,
gameStatus: GameInProgress,
}
return game
}
func (g *game) play() error {
var win bool
var symbol Symbol
for {
if g.firstPlayerTurn {
x, y, err := g.firstPlayer.getNextMove()
if err != nil {
return err
}
win, symbol, err = g.board.markSymbol(x, y, g.firstPlayer.getSymbol())
if err != nil {
return err
}
g.firstPlayerTurn = false
g.printMove(g.firstPlayer, x, y)
} else {
x, y, err := g.secondPlayer.getNextMove()
if err != nil {
return err
}
win, symbol, err = g.board.markSymbol(x, y, g.secondPlayer.getSymbol())
if err != nil {
return err
}
g.firstPlayerTurn = true
g.printMove(g.secondPlayer, x, y)
}
g.moveIndex = g.moveIndex + 1
g.setGameStatus(win, symbol)
if g.gameStatus != GameInProgress {
break
}
}
return nil
}
func (g *game) setGameStatus(win bool, symbol Symbol) {
if win {
if g.firstPlayer.getSymbol() == symbol {
g.gameStatus = FirstPlayerWin
return
} else if g.secondPlayer.getSymbol() == symbol {
g.gameStatus = SecondPlayerWin
return
}
}
if g.moveIndex == g.board.dimension*g.board.dimension {
g.gameStatus = GameDraw
return
}
g.gameStatus = GameInProgress
}
func (g *game) printMove(player iPlayer, x, y int) {
symbolString := ""
symbol := player.getSymbol()
if symbol == Cross {
symbolString = "*"
} else if symbol == Circle {
symbolString = "o"
}
fmt.Printf("Player %d Move with Symbol %s at Position X:%d Y:%d\n", player.getID(), symbolString, x, y)
g.board.printBoard()
fmt.Println("")
}
func (g *game) printResult() {
switch g.gameStatus {
case GameInProgress:
fmt.Println("Game in Between")
case GameDraw:
fmt.Println("Game Drawn")
case FirstPlayerWin:
fmt.Println("First Player Win")
case SecondPlayerWin:
fmt.Println("Second Player Win")
default:
fmt.Println("Invalid Game Status")
}
g.board.printBoard()
}Output
In the above program, we have fixed the moves for both the player in the humanPlayer.go file. Here is the output based upon those moves.
Player 1 Move with Symbol * at Position X:1 Y:1
...
.*.
...
Player 2 Move with Symbol o at Position X:1 Y:2
...
.*o
...
Player 1 Move with Symbol * at Position X:2 Y:0
...
.*o
*..
Player 2 Move with Symbol o at Position X:0 Y:2
..o
.*o
*..
Player 1 Move with Symbol * at Position X:2 Y:2
..o
.*o
*.*
Player 2 Move with Symbol o at Position X:0 Y:0
o.o
.*o
*.*
Player 1 Move with Symbol * at Position X:2 Y:1
o.o
.*o
***
First Player Win
o.o
.*o
***Full Working Code:
Here is the full working code in one file
main.go
package main
import "fmt"
type Symbol uint8
const (
Cross Symbol = iota
Circle
Dot
)
type GameStatus uint8
const (
GameInProgress GameStatus = iota
GameDraw
FirstPlayerWin
SecondPlayerWin
)
type iPlayer interface {
getSymbol() Symbol
getNextMove() (int, int, error)
getID() int
}
var (
MovesPlayer1 = [4][2]int{{1, 1}, {2, 0}, {2, 2}, {2, 1}}
MovesPlayer2 = [4][2]int{{1, 2}, {0, 2}, {0, 0}, {0, 0}}
)
type humanPlayer struct {
symbol Symbol
index int
id int
}
func (h *humanPlayer) getSymbol() Symbol {
return h.symbol
}
func (h *humanPlayer) getNextMove() (int, int, error) {
if h.symbol == Cross {
h.index = h.index + 1
return MovesPlayer1[h.index-1][0], MovesPlayer1[h.index-1][1], nil
} else if h.symbol == Circle {
h.index = h.index + 1
return MovesPlayer2[h.index-1][0], MovesPlayer2[h.index-1][1], nil
}
return 0, 0, fmt.Errorf("Invalid Symbol")
}
func (h *humanPlayer) getID() int {
return h.id
}
type computerPlayer struct {
symbol Symbol
id int
}
func (c *computerPlayer) getSymbol() Symbol {
return c.symbol
}
func (c *computerPlayer) getNextMove() (int, int, error) {
//To be implemented
return 0, 0, nil
}
func (c *computerPlayer) getID() int {
return c.id
}
type board struct {
square [][]Symbol
dimension int
}
func (b *board) printBoard() {
for i := 0; i < b.dimension; i++ {
for j := 0; j < b.dimension; j++ {
if b.square[i][j] == Dot {
fmt.Print(".")
} else if b.square[i][j] == Cross {
fmt.Print("*")
} else {
fmt.Print("o")
}
}
fmt.Println("")
}
}
func (b *board) markSymbol(i, j int, symbol Symbol) (bool, Symbol, error) {
if i > b.dimension || j > b.dimension {
return false, Dot, fmt.Errorf("index input is greater than dimension")
}
if b.square[i][j] != Dot {
return false, Dot, fmt.Errorf("input square already marked")
}
if symbol != Cross && symbol != Circle {
return false, Dot, fmt.Errorf("incorrect Symbol")
}
b.square[i][j] = symbol
win := b.checkWin(i, j, symbol)
return win, symbol, nil
}
func (b *board) checkWin(i, j int, symbol Symbol) bool {
//Check Row
rowMatch := true
for k := 0; k < b.dimension; k++ {
if b.square[i][k] != symbol {
rowMatch = false
}
}
if rowMatch {
return rowMatch
}
//Check Row
columnMatch := true
for k := 0; k < b.dimension; k++ {
if b.square[k][j] != symbol {
columnMatch = false
}
}
if columnMatch {
return columnMatch
}
//Check diagonal
diagonalMatch := false
if i == j {
diagonalMatch = true
for k := 0; k < b.dimension; k++ {
if b.square[k][k] != symbol {
diagonalMatch = false
}
}
}
return diagonalMatch
}
type game struct {
board *board
firstPlayer iPlayer
secondPlayer iPlayer
firstPlayerTurn bool
moveIndex int
gameStatus GameStatus
}
func initGame(b *board, p1, p2 iPlayer) *game {
game := &game{
board: b,
firstPlayer: p1,
secondPlayer: p2,
firstPlayerTurn: true,
gameStatus: GameInProgress,
}
return game
}
func (g *game) play() error {
var win bool
var symbol Symbol
for {
if g.firstPlayerTurn {
x, y, err := g.firstPlayer.getNextMove()
if err != nil {
return err
}
win, symbol, err = g.board.markSymbol(x, y, g.firstPlayer.getSymbol())
if err != nil {
return err
}
g.firstPlayerTurn = false
g.printMove(g.firstPlayer, x, y)
} else {
x, y, err := g.secondPlayer.getNextMove()
if err != nil {
return err
}
win, symbol, err = g.board.markSymbol(x, y, g.secondPlayer.getSymbol())
if err != nil {
return err
}
g.firstPlayerTurn = true
g.printMove(g.secondPlayer, x, y)
}
g.moveIndex = g.moveIndex + 1
g.setGameStatus(win, symbol)
if g.gameStatus != GameInProgress {
break
}
}
return nil
}
func (g *game) setGameStatus(win bool, symbol Symbol) {
if win {
if g.firstPlayer.getSymbol() == symbol {
g.gameStatus = FirstPlayerWin
return
} else if g.secondPlayer.getSymbol() == symbol {
g.gameStatus = SecondPlayerWin
return
}
}
if g.moveIndex == g.board.dimension*g.board.dimension {
g.gameStatus = GameDraw
return
}
g.gameStatus = GameInProgress
}
func (g *game) printMove(player iPlayer, x, y int) {
symbolString := ""
symbol := player.getSymbol()
if symbol == Cross {
symbolString = "*"
} else if symbol == Circle {
symbolString = "o"
}
fmt.Printf("Player %d Move with Symbol %s at Position X:%d Y:%d\n", player.getID(), symbolString, x, y)
g.board.printBoard()
fmt.Println("")
}
func (g *game) printResult() {
switch g.gameStatus {
case GameInProgress:
fmt.Println("Game in Between")
case GameDraw:
fmt.Println("Game Drawn")
case FirstPlayerWin:
fmt.Println("First Player Win")
case SecondPlayerWin:
fmt.Println("Second Player Win")
default:
fmt.Println("Invalid Game Status")
}
g.board.printBoard()
}
func main() {
board := &board{
square: [][]Symbol{{Dot, Dot, Dot}, {Dot, Dot, Dot}, {Dot, Dot, Dot}},
dimension: 3,
}
player1 := &humanPlayer{
symbol: Cross,
id: 1,
}
player2 := &humanPlayer{
symbol: Circle,
id: 2,
}
game := initGame(board, player1, player2)
game.play()
game.printResult()
}Output
In the above program as well, we have fixed the moves for both the player in the humanPlayer class. Here is the output based upon those moves.
Player 1 Move with Symbol * at Position X:1 Y:1
...
.*.
...
Player 2 Move with Symbol o at Position X:1 Y:2
...
.*o
...
Player 1 Move with Symbol * at Position X:2 Y:0
...
.*o
*..
Player 2 Move with Symbol o at Position X:0 Y:2
..o
.*o
*..
Player 1 Move with Symbol * at Position X:2 Y:2
..o
.*o
*.*
Player 2 Move with Symbol o at Position X:0 Y:0
o.o
.*o
*.*
Player 1 Move with Symbol * at Position X:2 Y:1
o.o
.*o
***
First Player Win
o.o
.*o
***Note: Check out our Golang Advanced Tutorial. The tutorials in this series are elaborative and we have tried to cover all concepts with examples. This tutorial is for those who are looking to gain expertise and a solid understanding of golang - Golang Advance Tutorial
Also if you are interested in understanding how all design patterns can be implemented in Golang. If yes, then this post is for you -All Design Patterns Golang