Spi-Ral-Toe

spiraltoe.go

package main

import "os"

var input [3]byte // 2nd index for enter key, 3rd for windoze
var spiral = []byte{1, 2, 3, 8, 9, 4, 7, 6, 5}
var unspiral = []byte{1, 2, 3, 6, 9, 8, 7, 4, 5}
var play func(byte, []rune)

func main() {
	play = func(move byte, board []rune) {
		update := func(next byte, board []rune, r rune) (done bool) {
			check := func(m []int) (winner bool) {
				for i := 0; i < 16; i += 2 {
					s := m[i]
					w := m[i+1]
					o := board[s]
					if o == board[w+s] && o == board[s+(w*2)] {
						winner = o > 0
					}
				}
				return
			}
			if board[next-1] > '9' {
				return false
			}
			board[next-1] = r
			println(string(r), "played", next)
			println(string(board)[:3])
			println(string(board)[3:6])
			println(string(board)[6:])
			// re: https://stackoverflow.com/questions/2245801/code-golf-tic-tac-toe/2565507
			if check([]int{0, 1, 3, 1, 6, 1, 0, 3, 1, 3, 2, 3, 0, 4, 2, 2}) {
				println("X won")
				return true
			}
			for _, r = range board {
				if r <= '9' {
					return false
				}
			}
			println("tie")
			return true
		}
		// credit to Martin Gardner: https://codegolf.stackexchange.com/questions/152064/play-tic-tac-toe-and-never-lose
		if update(unspiral[move+move%2*2-2], board, 'X') {
			return
		}
		os.Stdin.Read(input[:])
		if input[0] > 48 && input[0] < 58 {
			update(input[0]-48, board, 'O')
			play(spiral[input[0]-49], board)
		}
	}
	println("X always goes in the middle")
	play(10, []rune{'1', '2', '3', '4', '5', '6', '7', '8', '9'})
}