Zobrist Hash in Kotlin by the example of tic-tac-toe

Zobrist.kt

import kotlin.math.pow
import kotlin.random.Random

// Article: https://medium.com/@larswaechter/zobrist-hashing-305c6c3c54d0

/*
 * Build the Zobrist table with random numbers.
 * For 9 cells and 2 players we need 18 random numbers.
 */
fun buildZobristTable(): Array<Array<Long>> {
	val table = Array(2) { Array(9) { 0L } }

	for (i in 0..1)
		for (k in 0..8)
			table[i][k] = Random.nextLong(2F.pow(64).toLong())

	return table
}

val table = buildZobristTable()

/*
 * Player 1 = X => index 0 in table
 * Player 2 = O => index 1 in table
 *
 * X . O
 * X . .
 * . . .
 */
val board = arrayOf(1, 0, 2, 1, 0, 0, 0, 0, 0)
var zobristHash = 0L

// Generate Zobrist hash
for(i in board.indices)
	if(board[i] != 0)
		zobristHash = zobristHash xor table[board[i] - 1][i]

println(zobristHash)

/*
 * Player 2 (O) plays in cell #1
 *
 * X O O
 * X . .
 * . . .
 */
val board2 = arrayOf(1, 2, 2, 1, 0, 0, 0, 0, 0)

// We use the old zobrist hash and take the key of cell #1 for player 2 to calc the new one
val zobristHash2 = zobristHash xor table[1][1]
println(zobristHash2)