/*
* private void Set_Can_Win(TicTacToeDecisionNode ticTacToeDecisionNode, Player originalPlayer)
* {
* if(ticTacToeDecisionNode.IsWinForOriginalPlayer)
* {
* ticTacToeDecisionNode.CanWinNode = true;
* return;
* }
*
* if(ticTacToeDecisionNode.CurrentPlayer.Letter == originalPlayer.Letter)
* {
* // if I am making the next move and any children is a winning move or a "killer move" it is also a killer move
* foreach(var childNode in ChildNodes)
* {
* if(childNode.IsWinForOriginalPlayer || childNode.CanWinNode)
* {
* ticTacToeDecisionNode.CanWinNode = true;
* return;
* }
* }
* }
* else
* {
* // if the other player is the next move and all of their children are killer moves, it is a killer move
* // if any of them are not killer moves, then it is not a killer move
* foreach (var childNode in ticTacToeDecisionNode.ChildNodes)
* {
* Set_Can_Win(childNode, originalPlayer);
* if (childNode.CanWinNode == false)
* {
* ticTacToeDecisionNode.CanWinNode = false;
* return;
* }
* }
* ticTacToeDecisionNode.CanWinNode = true;
* return;
* }
* }
*
* private void Set_Will_Lose(TicTacToeDecisionNode ticTacToeDecisionNode, Player playerForNode)
* {
* // No more child nodes, check these nodes
* if (ticTacToeDecisionNode.GameState == GameState.Tie)
* {
* ticTacToeDecisionNode.IsLosingNodeForOriginalPlayer = false;
* return;
* }
* else if (ticTacToeDecisionNode.GameState == GameState.Win && ticTacToeDecisionNode.WinningPlayer.Letter == playerForNode.Letter)
* {
* ticTacToeDecisionNode.IsLosingNodeForOriginalPlayer = false;
* return;
* }
* else if (ticTacToeDecisionNode.GameState == GameState.Win && ticTacToeDecisionNode.WinningPlayer.Letter != playerForNode.Letter)
* {
* ticTacToeDecisionNode.IsLosingNodeForOriginalPlayer = true;
* return;
* }
*
* if (ticTacToeDecisionNode.GameState != GameState.InProgress && ticTacToeDecisionNode.ChildNodes.Count > 0)
* {
* throw new InvalidOperationException("Invalid state");
* }
*
* foreach (var childNode in ticTacToeDecisionNode.ChildNodes)
* {
* Set_Will_Lose(childNode, playerForNode);
*
* if (childNode.IsLosingNodeForOriginalPlayer == false)
* {
* ticTacToeDecisionNode.IsLosingNodeForOriginalPlayer = false;
* return;
* }
* }
*
* ticTacToeDecisionNode.IsLosingNodeForOriginalPlayer = true;
* }
*
* private void Set_Will_Win_Or_Tie(TicTacToeDecisionNode ticTacToeDecisionNode, Player playerForNode)
* {
* // No more child nodes, check these nodes
* if (ChildNodes.Count == 0)
* {
* if (ticTacToeDecisionNode.GameState == GameState.Win && ticTacToeDecisionNode.WinningPlayer.Letter == playerForNode.Letter)
* {
* ticTacToeDecisionNode.IsNonLosingNodeForOriginalPlayer = true;
* return;
* }
* else if (ticTacToeDecisionNode.GameState == GameState.Win && ticTacToeDecisionNode.WinningPlayer.Letter != playerForNode.Letter)
* {
* ticTacToeDecisionNode.IsNonLosingNodeForOriginalPlayer = false;
* return;
* }
* else if (ticTacToeDecisionNode.GameState == GameState.Tie)
* {
* ticTacToeDecisionNode.IsNonLosingNodeForOriginalPlayer = true;
* return;
* }
* }
*
* if (ticTacToeDecisionNode.GameState != GameState.InProgress && ticTacToeDecisionNode.ChildNodes.Count > 0)
* {
* throw new InvalidOperationException("Invalid state");
* }
*
* foreach (var childNode in ticTacToeDecisionNode.ChildNodes)
* {
* Set_Will_Win_Or_Tie(childNode, playerForNode);
* if (childNode.IsNonLosingNodeForOriginalPlayer == false)
* {
* ticTacToeDecisionNode.IsNonLosingNodeForOriginalPlayer = false;
* return;
* }
* }
*
* ticTacToeDecisionNode.IsNonLosingNodeForOriginalPlayer = true;
* }
*
* private static void Set_Will_Win(TicTacToeDecisionNode ticTacToeDecisionNode, Player originalPlayer)
* {
* // No more child nodes, check these nodes
* if (ticTacToeDecisionNode.ChildNodes.Count == 0)
* {
* if (ticTacToeDecisionNode.GameState == GameState.Tie)
* {
* ticTacToeDecisionNode.IsWinForOriginalPlayer = false;
* return;
* }
* else if (ticTacToeDecisionNode.GameState == GameState.Win && ticTacToeDecisionNode.WinningPlayer.Letter != originalPlayer.Letter)
* {
* ticTacToeDecisionNode.IsWinForOriginalPlayer = false;
* return;
* }
* else if (ticTacToeDecisionNode.GameState == GameState.Win && ticTacToeDecisionNode.WinningPlayer.Letter == originalPlayer.Letter)
* {
* ticTacToeDecisionNode.IsWinForOriginalPlayer = true;
* return;
* }
* }
*
* if (ticTacToeDecisionNode.GameState != GameState.InProgress && ticTacToeDecisionNode.ChildNodes.Count > 0)
* {
* throw new InvalidOperationException("Invalid state");
* }
*
* foreach (var childNode in ticTacToeDecisionNode.ChildNodes)
* {
* Set_Will_Win(childNode, originalPlayer);
* if(childNode.IsWinForOriginalPlayer == false)
* {
* ticTacToeDecisionNode.IsWinForOriginalPlayer = false;
* return;
* }
* }
*
* ticTacToeDecisionNode.IsWinForOriginalPlayer = true;
* }
*/
private void CreateChildNodes()
{
if (IsBoardInWinningState(ThisModel))
{
// don't add child nodes
GameState = GameState.Win;
//CurrentPlayer = null;
}
else if (IsBoardFull(ThisModel))
{
// don't add child nodes - game over with no winner
GameState = GameState.Tie;
//CurrentPlayer = null;
}
else
{
// there are still empty nodes
GameState = GameState.InProgress;
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
if (!ThisModel.Board.Squares[i, j].Played)
{
// Get the current player for the next turn
SquareLetter nextLetter = SquareLetter.O;
Player currentPlayer = ThisModel.Player1;
if (CurrentPlayerLetter == ThisModel.Player1.Letter)
{
nextLetter = this.ThisModel.Player2.Letter;
currentPlayer = this.ThisModel.Player2;
}
else
{
nextLetter = this.ThisModel.Player1.Letter;
currentPlayer = this.ThisModel.Player1;
}
// create a new game state for hypothetical move
var newGameState = new TicTacToeGameModel(ThisModel.Player1.PlayerType, ThisModel.Player2.PlayerType, ThisModel.Board, currentPlayer, i, j);
var childNode = new TicTacToeDecisionNode(newGameState, !IsOriginalPlayer, OriginalLetter, nextLetter, i, j);
ChildNodes.Add(childNode);
}
}
}
}
}
public static MoveModel GetBestMove(TicTacToeGameModel model)
{
//get the best move for the current player
TicTacToeGameModel fakeGameModel = null;
try
{
fakeGameModel = new TicTacToeGameModel(model.Player1.PlayerType, model.Player2.PlayerType, model.Board, model.CurrentPlayer);
}
catch (Exception e)
{
Console.WriteLine("Unable to create game model");
throw e;
}
TicTacToeDecisionNode decisionNode = null;
try
{
Player lastPlayer = fakeGameModel.Player1;
//use last player as current player
if (fakeGameModel.CurrentPlayer == fakeGameModel.Player1)
{
lastPlayer = fakeGameModel.Player2;
}
decisionNode = new TicTacToeDecisionNode(fakeGameModel, fakeGameModel.CurrentPlayer.Letter, lastPlayer.Letter);
}
catch (Exception e)
{
Console.WriteLine("Unable to create decision node");
throw e;
}
MoveModel bestMove = null;
try
{
bestMove = decisionNode.GetBestMove();
}
catch (Exception e)
{
Console.WriteLine("Unable to get best move");
throw e;
}
return(bestMove);
}
private static void SetNodeOutcome(TicTacToeDecisionNode node, bool isForOriginalPlayer, SquareLetter originalLetter)
{
if (node.GameState == GameState.Win && node.WinningPlayer.Letter == originalLetter)
{
node.Score = 100;
return;
}
else if (node.GameState == GameState.Win && node.WinningPlayer.Letter != originalLetter)
{
node.Score = -100;
return;
}
else if (node.GameState == GameState.Tie)
{
node.Score = 0;
return;
}
// check children
if (isForOriginalPlayer)
{
// get max
int max = int.MinValue;
foreach (var childNode in node.ChildNodes)
{
SetNodeOutcome(childNode, !isForOriginalPlayer, originalLetter);
max = Math.Max(max, childNode.Score);
}
node.Score = max;
return;
}
else
{
// get min
int min = int.MaxValue;
foreach (var childNode in node.ChildNodes)
{
SetNodeOutcome(childNode, !isForOriginalPlayer, originalLetter);
min = Math.Min(min, childNode.Score);
}
node.Score = min;
return;
}
}