private static short ScoreNode(GameTree leaf)
{
short score = 0;
switch (leaf.Data.State)
{
case GameState.Xwin:
score = 10000;
break;
case GameState.Owin:
score = -10000;
break;
case GameState.Draw:
score = 0;
break;
case GameState.Open:
var xWins = (short)(CountWins(Player.X, leaf.Data) * 10);
var oWins = (short)(CountWins(Player.O, leaf.Data) * 10);
score = (short)(xWins - oWins);
score = leaf.Data.GameBoard.Aggregate(score, (current, board) => (short)(current + CalculateScore(board)));
break;
}
leaf.Score = score;
return(score);
}
private UltimateTicTacToeMove MinMax()
{
var minMax = AlphaBeta(_gameTree, short.MinValue + 10, short.MaxValue - 10, Player == Player.X);
Debug.WriteLine($"MinMax:{minMax}, Low:{_gameTree.GetLeafNodes().Min(node => node.Score)}, High:{_gameTree.GetLeafNodes().Max(node => node.Score)}");
Debug.WriteLine($"I'm looking ahead {_gameTree.GetTreeDepth()} moves!");
var possibleMoves = _gameTree.Children.Where(child => child.Score == minMax);
// ReSharper disable PossibleMultipleEnumeration
var index = new Random().Next(0, possibleMoves.Count());
_gameTree = possibleMoves.ElementAt(index); //Update the game state to the move chosen
return(possibleMoves.ElementAt(index).Data.LastMove);
// ReSharper restore PossibleMultipleEnumeration
}
public UltimateTicTacToeMove TakeTurn(UltimateTicTacToeBoard ticTacToeBoard)
{
_taunt("Planning My Move...");
GameTree currentTree = _gameTree?.GetNode(ticTacToeBoard);
Debug.WriteLine($"There were {_gameTree?.GetNodeCount()} nodes in the tree prior to this move.");
//Taunt the player if they played well!
if (_gameTree?.Children != null && _gameTree.Children.Count != 0)
{
var lowScore = _gameTree.Children.Min(node => node.Score);
var highScore = _gameTree.Children.Max(node => node.Score);
var bestMove = Player == Player.O ? highScore : lowScore;
var worstMove = Player == Player.X ? highScore : lowScore;
var bestPlayedMoves = _gameTree.Children.Where(child => child.Score == bestMove);
var worstPlayedMoves = _gameTree.Children.Where(child => child.Score == worstMove);
var playedMoves = bestPlayedMoves as IList <GameTree> ?? bestPlayedMoves.ToList();
if (playedMoves.Contains(currentTree) && playedMoves.Count == 1 && Math.Abs(bestMove - worstMove) > 250)
{
_taunt("Nice Move Kiddums!");
Thread.Sleep(timeout: new TimeSpan(0, 0, 5));
}
else if (worstPlayedMoves.Contains(currentTree) && Math.Abs(bestMove - worstMove) > 250)
{
_taunt("What are you thinking?");
Thread.Sleep(timeout: new TimeSpan(0, 0, 5));
}
}
_gameTree = currentTree ?? new GameTree(data: ticTacToeBoard.Clone());
Debug.WriteLine($"Tree Triming reduced it to {_gameTree.GetNodeCount()} nodes.");
Debug.WriteLine($"Memory Used {GC.GetTotalMemory(false)}");
GC.Collect();
GC.WaitForPendingFinalizers();
Debug.WriteLine($"Memory Used {GC.GetTotalMemory(false)}");
PopulateTree();
Debug.WriteLine($"Memory Used {GC.GetTotalMemory(false)}");
Debug.WriteLine($"Tree population increased it to {_gameTree.GetNodeCount()} nodes at a depth of {_gameTree.GetTreeDepth()}.");
var move = MinMax();
return(move);
}
private static short AlphaBeta(GameTree node, short alpha, short beta, bool maximizingPlayer)
{
if (node.Children.Count == 0)
{
return(ScoreNode(node));
}
if (maximizingPlayer)
{
var value = short.MinValue;
foreach (var child in node.Children)
{
value = Math.Max(value, AlphaBeta(child, alpha, beta, false));
alpha = Math.Max(alpha, value);
if (beta < alpha)
{
break;
}
}
node.Score = value;
return(value);
}
else
{
var value = short.MaxValue;
foreach (var child in node.Children)
{
value = Math.Min(value, AlphaBeta(child, alpha, beta, true));
beta = Math.Min(beta, value);
if (beta < alpha)
{
break;
}
}
node.Score = value;
return(value);
}
}
