コンピュータと対戦できる！３目並べ（tic-toc-toe）をGo言語で実装してみよう

package main

import (
	"fmt"
	"math/rand"
)

func printBoard(board [][]int) {
	fmt.Println("--------------------")
	fmt.Println("  a b c")
	for i, row := range board {
		fmt.Print(i+1, " ")
		for _, v := range row {
			switch v {
			case 0:
				fmt.Print(". ")
			case 1:
				fmt.Print("X ")
			case -1:
				fmt.Print("O ")
			}
		}
		fmt.Println()
	}
}

func getInput() (int, int) {
	var s string
	fmt.Scan(&s)
	x, y := 0, 0
	if '0' <= s[0] && s[0] <= '9' {
		y = int(s[0]-'0') - 1
		x = int(s[1] - 'a')
	} else {
		y = int(s[1]-'0') - 1
		x = int(s[0] - 'a')
	}
	return x, y
}

func checkWin(board [][]int) int {
	for i := 0; i < 3; i++ {
		if board[i][0] != 0 && board[i][0] == board[i][1] && board[i][0] == board[i][2] {
			return board[i][0]
		}
		if board[0][i] != 0 && board[0][i] == board[1][i] && board[0][i] == board[2][i] {
			return board[0][i]
		}
	}
	if board[0][0] != 0 && board[0][0] == board[1][1] && board[0][0] == board[2][2] {
		return board[0][0]
	}
	if board[0][2] != 0 && board[0][2] == board[1][1] && board[0][2] == board[2][0] {
		return board[0][2]
	}
	return 0
}

// 最初に見つけた場所に置く
func thinkSeq(board [][]int) (int, int) {

	for i := 0; i < 3; i++ {
		for j := 0; j < 3; j++ {
			if board[i][j] == 0 {
				return j, i
			}
		}
	}
	return 0, 0
}

type pos struct {
	x, y int
}

// ランダムに置く場所を決める
func thinkRandom(board [][]int) (int, int) {
	p := []pos{}
	for i := 0; i < 3; i++ {
		for j := 0; j < 3; j++ {
			if board[i][j] == 0 {
				p = append(p, pos{j, i})
			}
		}
	}
	sel := rand.Intn(len(p))
	return p[sel].x, p[sel].y
}

// 負けない様ににする
func thinkStop2(boaard [][]int, turn int) (int, int) {
	fmt.Println("turn", turn)
	p := []pos{}
	for i := 0; i < 3; i++ {
		for j := 0; j < 3; j++ {
			if boaard[i][j] != 0 {
				continue
			}
			boaard[i][j] = -turn
			if checkWin(boaard) == -turn {
				boaard[i][j] = 0
				return j, i
			}
			boaard[i][j] = 0
			p = append(p, pos{j, i})
		}
	}
	sel := rand.Intn(len(p))
	return p[sel].x, p[sel].y
}

// 深さ優先探索で、最終的な勝者を返す
func think(board [][]int, turn int) (int, int, int) {
	// 9マス全てが埋まっているかどうか確認
	cnt := 0
	for i := 0; i < 3; i++ {
		for j := 0; j < 3; j++ {
			if board[i][j] == 0 {
				cnt++
			}
		}
	}
	if cnt == 0 {
		return -1, -1, 0 // 全て埋まっていればDRAW
	}

	x, y := 0, 0
	win := false
	res := -turn
	for i := 0; i < 3; i++ {
		for j := 0; j < 3; j++ {
			if board[i][j] != 0 {
				continue // 既に置かれている場合はスキップ
			}
			board[i][j] = turn
			winner := checkWin(board)
			if winner == turn {
				board[i][j] = 0
				return j, i, turn
			}
			_, _, r := think(board, -turn)
			board[i][j] = 0

			if r == turn { // 自分が勝つ場合は、その手を覚える
				win = true
				x, y = j, i
				res = turn
			}
			if win == false { // 自分の価値が決定してない場合
				if r == 0 { // 引き分けの場合は、手を覚える
					x, y = j, i
					res = 0
				}
				if r == -turn && res == -turn { //現在まだ引き分け以上の手が見つかっていなければ、場所を記録
					x, y = j, i
				}
			}
		}
	}
	return x, y, res
}

func main() {
	board := [][]int{
		{0, 0, 0},
		{0, 0, 0},
		{0, 0, 0},
	}

	for i := 0; i < 9; i++ {
		printBoard(board)
		winner := checkWin(board)
		if winner != 0 {
			fmt.Println("--------------------")
			if winner == 1 {
				fmt.Println("Winner is player1")
			}
			if winner == -1 {
				fmt.Println("Winner is player2")
			}
			fmt.Println("--------------------")

			return
		}

		var x, y int
		if i%2 == 0 {
			for true {
				fmt.Print("Enter position(ex. 1a):")
				x, y = getInput()
				if board[y][x] != 0 {
					fmt.Println("already occupied. try again.")
				} else {
					break
				}
			}
		} else {
			// x, y = thinkSeq(board)
			// x, y = thinkRandom(board)
			// x, y = thinkStop2(board, 1)
			x, y, _ = think(board, 1)
		}
		if i%2 == 0 {
			board[y][x] = -1
		} else {
			board[y][x] = 1
		}

	}

	printBoard(board)

	fmt.Println("--------------------")
	fmt.Println("Draw")
	fmt.Println("--------------------")
}