minimax.scala

	// static evaluate function
	// adapted from http://kartikkukreja.wordpress.com/2013/03/30/heuristic-function-for-tic-tac-toe/
	// original author : Kartik Kukreja

	val wins = Array(	Array(0,1,2), Array(3,4,5), Array(6,7,8),
				Array(0,3,6), Array(1,4,7), Array(2,5,8),
				Array(0,4,8), Array(2,4,6) )

	val heuristic = Array( 	Array(0,  -10, -100, -1000),
				Array(10,   0,    0 ,    0),
			        Array(100,  0,    0,     0),
			        Array(1000, 0,    0,     0) )

	// good = positive numbers, bad = negative numbers
	def evaluatePosition(board:Array[Int], player:Int):Int = {
		val opponent:Int = player*(-1)
		
		var players = 0
		var others = 0
		var total = 0
		
		for(i <- wins){
			players = 0
			others = 0
			for(j <- i){
				if (board(j) == player){
					players += 1
				}else if(board(j) == opponent){
					others += 1
				}
			}
			
			total += heuristic(players)(others)
		}
		
		total
	}
	
	// X = -1 max player, O = 1 min player
	def minmax(board:Array[Int], height:Int, player:Int):Double={
		if(height == 0)
			evaluatePosition(board, player)
		
		var alpha = -player * Double.PositiveInfinity;
		
		val allBoards = makeAllPossibleMoves(board, player) // array of all child boards
		for(b <- allBoards){
			val score = minmax(b, height-1, -player)
			alpha = if (player == -1) Math.max(alpha, score) else Math.min(alpha, score)
		}
		
		alpha
	}