private int minimax(Desk desk, GameRules rules, int depth, short currentPlayer, bool maximizingPlayer)
{
movesInspected++;
short oppositePlayer = rules.getOppositePlayer(currentPlayer);
if (rules.isGameEnd(desk)) //check game end - both players have some fields and at least one can move
{
short nextPlayer = rules.getNextPlayer(desk);
if (desk.getPlayerFields(GameVar.PLAYER_WHITE).Count != 0 && desk.getPlayerFields(GameVar.PLAYER_BLACK).Count != 0 && nextPlayer == -1)
{
return(0); //draw, neither of players can move
}
if (maximizingPlayer)
{
return(int.MinValue + depthMax - depth);
}
return(int.MaxValue - depthMax + depth);
}
if (depth == 0) //check depth level, return eval of current position
{
if (maximizingPlayer)
{
return(-rules.getGameEvaluation(desk, oppositePlayer));
}
return(rules.getGameEvaluation(desk, oppositePlayer));
}
//get new possible moves, make the moves and call recursively minmax
ArrayList possibleMoves = rules.getPossibleMoves(desk, currentPlayer);
int bestVal = 0;
int currentVal = 0;
//current player has no possible moves, play "nothing" and call minimax
if (possibleMoves.Count == 0)
{
if (maximizingPlayer)
{
bestVal = int.MinValue;
currentVal = minimax(desk, rules, depth, oppositePlayer, false);
bestVal = Math.Max(bestVal, currentVal);
}
else
{
bestVal = int.MaxValue;
currentVal = minimax(desk, rules, depth, oppositePlayer, true);
bestVal = Math.Min(bestVal, currentVal);
}
return(bestVal);
}
if (maximizingPlayer) //current player's best move, looking for the highest rating move
{
bestVal = int.MinValue;
foreach (Move move in possibleMoves)
{
desk.makeMove(move);
currentVal = minimax(desk, rules, depth - 1, oppositePlayer, false);
desk.undoMove(move);
bestVal = Math.Max(bestVal, currentVal);
}
}
else //opposite player's best move - the worst move for current player, looking for the lowest rating move
{
bestVal = int.MaxValue;
foreach (Move move in possibleMoves)
{
desk.makeMove(move);
currentVal = minimax(desk, rules, depth - 1, oppositePlayer, true);
desk.undoMove(move);
bestVal = Math.Min(bestVal, currentVal);
}
}
return(bestVal);
}