/// <summary>
/// Generates a random, unpredictable move.
/// </summary>
/// <returns>Returns a move structure with defined X, Y coordinates.</returns>
private Move GenerateMediumDifficultyMove()
{
bool isValidMoveFound = false;
Move mediumDifficultyMove = new Move();
while (!isValidMoveFound)
{
// Generate random coordinates
mediumDifficultyMove.X = RandomGenerator.Next(0, Tictactoe.GetBoardHorizontalSize());
mediumDifficultyMove.Y = RandomGenerator.Next(0, Tictactoe.GetBoardVerticalSize());
// Check if the field is empty
if (IsBoardFieldEmpty(Board, mediumDifficultyMove.X, mediumDifficultyMove.Y))
{
isValidMoveFound = true;
}
}
return(mediumDifficultyMove);
}
/// <summary>
/// Generates the best move available using the negamax algorithm.
/// </summary>
/// <param name="board">Board on which to do the calculations.</param>
/// <param name="playerMark">Mark of the player who is calling the function.</param>
/// <returns>An optimal move for the given board and player.</returns>
/// Can be upgraded with alpha-beta pruning to increase performance.
private Move GenerateImpossibleDifficultyMove(string[,] board, string playerMark)
{
// Set the oponent players mark
string oponentPlayerMark = (playerMark == Resources.BoardCrossMark) ? Resources.BoardCircleMark : Resources.BoardCrossMark;
// Check if the player calling the function has won
if (Tictactoe.HasPlayerWon(board, playerMark))
{
return(new Move()
{
Value = 1
});
}
// Check if the player calling the function has lost
if (Tictactoe.HasPlayerWon(board, oponentPlayerMark))
{
return(new Move()
{
Value = -1
});
}
// Check for a draw
if (Tictactoe.HavePlayersDraw(board))
{
return(new Move()
{
Value = 0
});
}
// Set initial bestMove value to -2 because thats lower than the lowest possible value you can generate for a valid move from this implementation (which is -1)
var bestMove = new Move()
{
Value = -2
};
// Loop through the board
for (int i = 0; i < Tictactoe.GetBoardHorizontalSize(); i++)
{
for (int j = 0; j < Tictactoe.GetBoardVerticalSize(); j++)
{
if (IsBoardFieldEmpty(board, i, j))
{
// Mark the board field
board[i, j] = playerMark;
// Assign a new value to the opposite of a recursive function call
int value = -GenerateImpossibleDifficultyMove(board, oponentPlayerMark).Value;
// Store move information if it has better value than the current best move
if (value > bestMove.Value)
{
bestMove.Value = value;
bestMove.X = i;
bestMove.Y = j;
}
// Change the board field back to empty
board[i, j] = Resources.BoardEmptyField;
}
}
}
return(bestMove);
}
