// Recursive part of iterative deepening
private Tuple<Move, bool> RecursiveIterativeDeepening(State state, int depth, double alpha, double beta, int timeLimit, Stopwatch timer, Deck deck)
{
Move bestMove;
if (depth == 0 || state.IsGameOver())
{
if (state.Player == GameEngine.PLAYER)
{
bestMove = new PlayerMove(); // default constructor creates dummy action
bestMove.Score = AI.Evaluate(state);
return new Tuple<Move, Boolean>(bestMove, true);
}
else if (state.Player == GameEngine.COMPUTER)
{
bestMove = new ComputerMove(); // default constructor creates dummy action
bestMove.Score = AI.Evaluate(state);
return new Tuple<Move, Boolean>(bestMove, true);
}
else
{
throw new Exception();
}
}
if (state.Player == GameEngine.PLAYER){
bestMove = new PlayerMove();
double highestScore = Double.MinValue, currentScore = Double.MinValue;
List<Move> moves = state.GetAllMoves();
foreach (Move move in moves)
{
State resultingState = state.ApplyMove(move);
currentScore = RecursiveIterativeDeepening(resultingState, depth - 1, alpha, beta, timeLimit, timer, deck).Item1.Score;
if (currentScore > highestScore)
{
highestScore = currentScore;
bestMove = (PlayerMove)move;
}
alpha = Math.Max(alpha, highestScore);
if (beta <= alpha)
break;
if (timer.ElapsedMilliseconds > timeLimit)
{
bestMove.Score = highestScore;
return new Tuple<Move, Boolean>(bestMove, false); // recursion not completed, return false
}
}
bestMove.Score = highestScore;
return new Tuple<Move, Boolean>(bestMove, true);
}
else
{
bestMove = new ComputerMove();
double lowestScore = Double.MaxValue, currentScore = Double.MaxValue;
List<Move> moves = null;
if (depth == definedDepth - 1)
{
int nextCard = game.nextCard;
moves = state.GetAllComputerMoves(nextCard);
}
else
{
if (deck.IsEmpty()) deck = new Deck();
moves = state.GetAllComputerMoves(deck);
}
foreach (Move move in moves)
{
deck.Remove(((ComputerMove)move).Card);
State resultingState = state.ApplyMove(move);
currentScore = RecursiveIterativeDeepening(resultingState, depth - 1, alpha, beta, timeLimit, timer, deck).Item1.Score;
if (currentScore < lowestScore)
{
lowestScore = currentScore;
bestMove = (ComputerMove)move;
}
beta = Math.Min(beta, lowestScore);
if (beta <= alpha)
break;
deck.Add(((ComputerMove)move).Card);
if (timer.ElapsedMilliseconds > timeLimit)
{
bestMove.Score = lowestScore;
return new Tuple<Move, Boolean>(bestMove, false); // recursion not completed, return false
}
}
bestMove.Score = lowestScore;
return new Tuple<Move, Boolean>(bestMove, true);
}
}
// MIN part of Minimax
Move Min(State state, int depth, double alpha, double beta)
{
ComputerMove bestMove = new ComputerMove();
double lowestScore = Double.MaxValue, currentScore = Double.MaxValue;
List<Move> moves = null;
if (depth == definedDepth - 1)
{
int nextCard = game.nextCard;
moves = state.GetAllComputerMoves(nextCard);
}
else
{
if (deck.IsEmpty()) deck = new Deck();
moves = state.GetAllComputerMoves(deck);
}
foreach (Move move in moves)
{
deck.Remove(((ComputerMove)move).Card);
State resultingState = state.ApplyMove(move);
currentScore = MinimaxAlgorithm(resultingState, depth - 1, alpha, beta, deck).Score;
if (currentScore < lowestScore)
{
lowestScore = currentScore;
bestMove = (ComputerMove)move;
}
beta = Math.Min(beta, lowestScore);
if (beta <= alpha)
break;
deck.Add(((ComputerMove)move).Card);
}
bestMove.Score = lowestScore;
return bestMove;
}
// Classic Minimax using alpha-beta pruning
private Move MinimaxAlgorithm(State state, int depth, double alpha, double beta, Deck deck)
{
Move bestMove;
if (depth == 0 || state.IsGameOver())
{
if (state.Player == GameEngine.PLAYER)
{
bestMove = new PlayerMove(); // default constructor creates dummy action
bestMove.Score = AI.Evaluate(state);
return bestMove;
}
else if (state.Player == GameEngine.COMPUTER)
{
bestMove = new ComputerMove(); // default constructor creates dummy action
bestMove.Score = AI.Evaluate(state);
return bestMove;
}
else
{
throw new Exception();
}
}
if (state.Player == GameEngine.PLAYER)
return Max(state, depth, alpha, beta);
else
return Min(state, depth, alpha, beta);
}
// Generates a new card on the board
private void GenerateNewCard()
{
int numTiles = 0;
int card = 0;
if (nextIsBonus)
{
List<int> possibleBonusCards = currentState.GeneratePossibleBonusCards();
card = possibleBonusCards[random.Next(0, possibleBonusCards.Count)];
numTiles = possibleBonusCards.Count * currentState.columnsOrRowsWithMovedTiles.Count;
}
else
{
card = deck.DealCard();
numTiles = currentState.columnsOrRowsWithMovedTiles.Count * 3;
}
// decide on position to put new tile
int row = 0, column = 0;
int index = random.Next(0, currentState.columnsOrRowsWithMovedTiles.Count); // random index of list of possible rows/columns
if (((PlayerMove)currentState.GeneratingMove).Direction == DIRECTION.LEFT)
{
row = currentState.columnsOrRowsWithMovedTiles[index];
column = 3; // right-most column
}
else if (((PlayerMove)currentState.GeneratingMove).Direction == DIRECTION.RIGHT)
{
row = currentState.columnsOrRowsWithMovedTiles[index];
column = 0; // left-most column
}
else if (((PlayerMove)currentState.GeneratingMove).Direction == DIRECTION.UP)
{
column = currentState.columnsOrRowsWithMovedTiles[index];
row = 0; // down-most row
}
else if (((PlayerMove)currentState.GeneratingMove).Direction == DIRECTION.DOWN)
{
column = currentState.columnsOrRowsWithMovedTiles[index];
row = 3; // up-most row
}
currentState.Grid[column][row] = card;
ComputerMove move = new ComputerMove(card, new Tuple<int, int>(column, row));
currentState.GeneratingMove = move;
}
