/// <summary>
/// Move quality
/// -1 worst move
/// 0 illegal move
/// +1 best move
/// </summary>
public static int MoveQuality(this TicTacToePosition position, TicTacToeLocation move)
{
if (position is null)
{
return(0);
}
if (move is null)
{
return(0);
}
var actual = MoveExpectation(position, move);
if (actual == GameOutcome.Illegal)
{
return(0);
}
var best = ExpectedWinner(position);
if (best == actual)
{
return(1);
}
else
{
return(-1);
}
}
/// <summary>
/// Move Degree, winning, loosing etc.
/// </summary>
public static MoveExpectancy MoveDegree(this TicTacToePosition position, TicTacToeLocation move)
{
if (position is null)
{
return(MoveExpectancy.Illegal);
}
if (move is null)
{
return(MoveExpectancy.Illegal);
}
if (!position.IsLegalMove(move, true))
{
return(MoveExpectancy.Illegal);
}
var expectation = MoveExpectation(position, move);
if (expectation == GameOutcome.Illegal)
{
return(MoveExpectancy.Illegal);
}
if (position.WhoIsOnMove == Mark.Cross)
{
if (expectation == GameOutcome.FirstWin)
{
return(MoveExpectancy.Win);
}
else if (expectation == GameOutcome.Draw)
{
return(MoveExpectancy.Draw);
}
else if (expectation == GameOutcome.SecondWin)
{
return(MoveExpectancy.Lose);
}
}
else
{
if (expectation == GameOutcome.FirstWin)
{
return(MoveExpectancy.Lose);
}
else if (expectation == GameOutcome.Draw)
{
return(MoveExpectancy.Draw);
}
else if (expectation == GameOutcome.SecondWin)
{
return(MoveExpectancy.Win);
}
}
return(MoveExpectancy.Illegal);
}
/// <summary>
/// Expected Winner
/// </summary>
public static GameOutcome ExpectedWinner(this TicTacToePosition position)
{
if (position is null)
{
return(GameOutcome.Illegal);
}
return(s_Outcomes.TryGetValue(position, out var result)
? result
: GameOutcome.Illegal);
}
/// <summary>
/// Move Expectation
/// </summary>
public static GameOutcome MoveExpectation(this TicTacToePosition position, TicTacToeLocation move)
{
if (position is null)
{
return(GameOutcome.Illegal);
}
if (move is null)
{
return(GameOutcome.Illegal);
}
return(ExpectedWinner(position.MakeMove(move)));
}
/// <summary>
/// Best Moves (all winning moves or, if the position drawish, all draw moves)
/// </summary>
public static TicTacToeLocation[] BestMoves(this TicTacToePosition position)
{
if (position is null)
{
return(Array.Empty <TicTacToeLocation>());
}
return(position
.AvailableMoves()
.Where(move => MoveQuality(position, move) == 1)
.OrderBy(move => move)
.ToArray());
}
private static void CoreUpdate()
{
s_Outcomes = TicTacToePosition
.AllLegalPositions()
.ToDictionary(p => p, p => GameOutcome.None);
var data = s_Outcomes
.Keys
.OrderByDescending(key => key.MarkCount);
foreach (var position in data)
{
if (position.Outcome != GameOutcome.None)
{
s_Outcomes[position] = position.Outcome;
continue;
}
var onMove = position.WhoIsOnMove;
GameOutcome bestOutcome = onMove == Mark.Cross
? GameOutcome.SecondWin
: GameOutcome.FirstWin;
foreach (var next in position.AvailablePositions())
{
GameOutcome outcome = s_Outcomes[next];
bestOutcome = onMove == Mark.Cross
? bestOutcome.BestForFirst(outcome)
: bestOutcome.BestForSecond(outcome);
}
s_Outcomes[position] = bestOutcome;
}
}
