/*
* Depth 2 is easy to win
* Depth 3 is somewhat harder to win
* Depth 4 is hard to win
* Depth 5 is unbeatable
* Depth 6 is smarter and can win in more situations
*/
protected byte NextMove(GameManager gameManager, byte distanceFromEnd)
{
byte move;
var choiceTree = new ChoiceTree();
var bestChoice = this.Minimax(gameManager, distanceFromEnd);
// Console.WriteLine(Newtonsoft.Json.JsonConvert.SerializeObject(choiceTree));
if (bestChoice == null)
{
move = (byte)gameManager.GetRemainingMoves().First();
}
else
{
move = bestChoice.Move;
}
return(move);
}
private Choice Minimax(GameManager gameManager, byte maxDistanceFromEnd, byte?distanceFromEnd = null, sbyte?alpha = null, sbyte?beta = null, bool maximizingPlayer = true, ChoiceTree choiceTree = null)
{
if (distanceFromEnd == null)
{
distanceFromEnd = maxDistanceFromEnd;
}
sbyte?bestValue = null;
byte? bestMove = null;
var moves = gameManager.GetRemainingMoves();
var bestChoices = new List <Choice>();
if (choiceTree != null)
{
choiceTree.Choices = new List <ChoiceTreeEl>();
choiceTree.EndChoices = new List <Choice>();
}
foreach (byte currMove in moves)
{
gameManager.NewMove(currMove, maximizingPlayer ? this : gameManager.GetOpponent(this));
sbyte?currValue = null;
if (gameManager.IsGameOver)
{
currValue = (gameManager.Winner == this)
? (sbyte)(10 + distanceFromEnd)
: (gameManager.Winner == null) ? (sbyte)(-distanceFromEnd) : (sbyte)(-10 - distanceFromEnd);
if (choiceTree != null)
{
choiceTree.EndChoices.Add(new Choice()
{
Value = (sbyte)currValue, Move = (byte)currMove
});
}
}
else if (distanceFromEnd > 0)
{
ChoiceTree currChoiceTree = null;
Choice currChoice = null;
if (choiceTree != null)
{
currChoice = new Choice()
{
Move = currMove
};
currChoiceTree = new ChoiceTree();
choiceTree.Choices.Add(new ChoiceTreeEl()
{
Choice = currChoice, ChoiceTree = currChoiceTree
});
}
var choice = this.Minimax(gameManager, maxDistanceFromEnd, (byte)(distanceFromEnd - 1), alpha, beta, !maximizingPlayer, currChoiceTree);
if (choice != null)
{
currValue = choice.Value;
currValue = (currValue == 9) ? -9 : ((currValue == -9) ? 9 : currValue);
if (choiceTree != null)
{
currChoice.Value = (sbyte)currValue;
}
}
else
{
Console.WriteLine("impossible");
}
}
else
{
currValue = (sbyte)(maximizingPlayer ? -9 : 9);
if (choiceTree != null)
{
choiceTree.EndChoices.Add(new Choice()
{
Value = (sbyte)currValue, Move = (byte)currMove
});
}
}
if (currValue != null)
{
if (bestValue == null ||
(maximizingPlayer && currValue > bestValue) ||
(!maximizingPlayer && currValue < bestValue))
{
bestChoices.Clear();
bestChoices.Add(new Choice()
{
Value = (sbyte)currValue, Move = (byte)currMove
});
bestValue = currValue;
bestMove = currMove;
}
else if (currValue == bestValue)
{
bestChoices.Add(new Choice()
{
Value = (sbyte)currValue, Move = (byte)currMove
});
bestValue = currValue;
bestMove = currMove;
}
if (maximizingPlayer)
{
if (alpha == null || currValue > alpha)
{
alpha = currValue;
}
}
else
{
if (beta == null || currValue < beta)
{
beta = currValue;
}
}
if (alpha != null &&
beta != null &&
beta < alpha)
{
gameManager.NewMove(currMove, null);
break;
}
}
gameManager.NewMove(currMove, null);
}
Choice bestChoice;
// Console.WriteLine(Newtonsoft.Json.JsonConvert.SerializeObject(bestChoices));
// Prever blocking moves
if (bestChoices.Count > 1)
{
if (distanceFromEnd == maxDistanceFromEnd)
{
var counts = new Dictionary <Choice, byte>();
var bestCount = 0;
bestChoices.ForEach(choice =>
{
byte count = 0;
var move = choice.Move;
gameManager.GetContainingPaths(move).ForEach(path =>
{
var otherCells = path.Where(cell => cell != move)
.GroupBy(cell => gameManager.GetCellOwner(cell))
.Select(group => new { Owner = group.Key, Cells = group.ToList() })
.ToList();
if (otherCells.Count == 1 &&
otherCells[0].Owner != null)
{
count++;
}
});
if (count > bestCount)
{
bestCount = count;
}
counts.Add(choice, count);
});
bestChoices = counts
.Keys
.Where(choice => counts[choice] == bestCount)
.ToList();
}
if (bestChoices.Count == 1)
{
bestChoice = bestChoices[0];
}
else
{
var rand = new Random();
var randNum = (byte)rand.Next(bestChoices.Count);
bestChoice = bestChoices[randNum];
}
}
else
{
bestChoice = new Choice()
{
Value = (sbyte)bestValue, Move = (byte)bestMove
};
}
if (choiceTree != null)
{
choiceTree.BestChoice = bestChoice;
}
return((bestValue == null)
? null
: bestChoice);
}