/// <summary>
/// Executed when it is the AI's turn if the AI is being used.
/// </summary>
IEnumerator AITurn()
{
MinimaxPair <Player[], double> moveToMake = Minimax(playerMap, difficulty, true);
Player[] nextBoard = moveToMake.bestMove;
int movePos = GetNextMove(playerMap, nextBoard);
MakeMove(playerMap, ai, movePos);
SetPly(human);
while (ply == ai)
{
yield return(null);
}
// COMMENT EVERYTHING ABOVE FOR A HUMAN VS. HUMAN GAME
// COMMENT EVERYTHING BELOW FOR A HUMAN VS. AI GAME
//if (Input.GetMouseButtonUp(0))
//{
// int clickedSquare = GetClickedSquare();
// List<int> legalMoves = GetLegalMoves(playerMap, ai);
// if (clickedSquare > -1 && legalMoves.Contains(clickedSquare))
// {
// MakeMove(playerMap, ply, clickedSquare);
// SetPly(human);
// }
//}
//while (ply == ai) yield return null;
}
/// <summary>
/// Minimax algorithm for the AI.
/// </summary>
/// <param name="boardMap">A 64-indexed list of Players representing a board, where each square is a player.</param>
/// <param name="depth">The number of moves the AI will look ahead.</param>
/// <param name="maximizingPlayer">True if calculating own score, false if calculating opposing player's score.</param>
/// <returns>A MinimaxPair object containing the best board and its score</returns>
MinimaxPair <Player[], double> Minimax(Player[] boardMap, int depth, bool maximizingPlayer)
{
Player[] gameTreeMap = CopyPlayerMap(boardMap);
List <int> legalMoves;
if (maximizingPlayer)
{
legalMoves = GetLegalMoves(gameTreeMap, ai);
}
else
{
legalMoves = GetLegalMoves(gameTreeMap, human);
}
if (legalMoves.Count == 0 || depth == 0)
{
return(new MinimaxPair <Player[], double>(gameTreeMap, Evaluate(gameTreeMap)));
}
MinimaxPair <Player[], double> bestBoard = new MinimaxPair <Player[], double>();
if (maximizingPlayer)
{
bestBoard.bestScore = Mathf.NegativeInfinity;
foreach (int legalMove in legalMoves)
{
MakeMove(gameTreeMap, ply, legalMove);
Player[] newGameTreeMap = CopyPlayerMap(gameTreeMap);
MinimaxPair <Player[], double> nextMove = Minimax(newGameTreeMap, depth - 1, false);
if (nextMove.bestScore > bestBoard.bestScore)
{
bestBoard.bestMove = nextMove.bestMove;
bestBoard.bestScore = nextMove.bestScore;
}
}
return(bestBoard);
}
else
{
bestBoard.bestScore = Mathf.Infinity;
foreach (int legalMove in legalMoves)
{
MakeMove(gameTreeMap, ply, legalMove);
Player[] newGameTreeMap = CopyPlayerMap(gameTreeMap);
MinimaxPair <Player[], double> nextMove = Minimax(newGameTreeMap, depth - 1, true);
if (nextMove.bestScore < bestBoard.bestScore)
{
bestBoard.bestMove = nextMove.bestMove;
bestBoard.bestScore = nextMove.bestScore;
}
}
return(bestBoard);
}
}
