// We assume Winner field is updated and correct => No need to recalculate winner
int Evaluate(GameBoardState boardState, PlayerTurn maxTurn, int currentDepth, int maxDepth)
{
bool maximizing = boardState.CurrentTurn == maxTurn;
if (currentDepth == maxDepth || boardState.Winner != null)
{
return(EvaluateHeuristic(boardState, maxTurn));
}
List <GameAction> possibleActions = GameLogicUtils.GetAllAvailableActions(boardState);
int evaluation;
if (maximizing)
{
int maxEvaluation = int.MinValue;
foreach (GameAction action in possibleActions)
{
GameBoardState afterMove = gameLogic.ApplyAction(boardState, action);
int afterMoveEvaluation = Evaluate(afterMove, maxTurn, currentDepth + 1, maxDepth);
if (afterMoveEvaluation > maxEvaluation)
{
maxEvaluation = afterMoveEvaluation;
}
}
evaluation = maxEvaluation;
}
else
{
int minEvaluation = int.MaxValue;
foreach (GameAction action in possibleActions)
{
GameBoardState afterMove = gameLogic.ApplyAction(boardState, action);
int afterMoveEvaluation = Evaluate(afterMove, maxTurn, currentDepth + 1, maxDepth);
if (afterMoveEvaluation < minEvaluation)
{
minEvaluation = afterMoveEvaluation;
}
}
evaluation = minEvaluation;
}
return(evaluation);
}
public GameAction CalculateComputerMove(GameBoardState gameState, GameDifficulty difficulty)
{
int maxDepth = ToRecursiveDepth(difficulty);
PlayerTurn maxTurn = gameState.CurrentTurn;
List <GameAction> possibleActions = GameLogicUtils.GetAllAvailableActions(gameState);
int maxEvaluation = int.MinValue;
GameAction bestMove = null;
foreach (GameAction action in possibleActions)
{
GameBoardState afterMove = gameLogic.ApplyAction(gameState, action);
int afterMoveEvaluation = Evaluate(afterMove, maxTurn, 0, maxDepth);
if (afterMoveEvaluation > maxEvaluation || (afterMoveEvaluation >= maxEvaluation && bestMove == null))
{
maxEvaluation = afterMoveEvaluation;
bestMove = action;
}
}
return(bestMove);
}
public GameAction CalculateComputerMove(GameBoardState gameState, GameDifficulty difficulty)
{
List <GameAction> actions = GameLogicUtils.GetAllAvailableActions(gameState);
return(actions[rand.Next(0, actions.Count)]);
}