/// <summary>
/// Undoes the last move, restoring the game to its state before the move was applied.
/// </summary>
public void UndoLastMove()
{
OthelloMove m = MoveHistory[MoveHistory.Count - 1] as OthelloMove;
// Note: there is a bug in this code.
if (!m.IsPass)
{
// Reset the board at the move's position.
mBoard[m.Position.Row, m.Position.Col] = 0;
Value += mCurrentPlayer;
Weight += mCurrentPlayer * mWeights[m.Position.Row, m.Position.Col];
// Iterate through the move's recorded flipsets.
foreach (var flipSet in m.FlipSets)
{
BoardPosition pos = m.Position;
// For each flipset, walk along the flipset's direction resetting pieces.
for (int i = 1; i <= flipSet.Count; i++)
{
pos = pos.Translate(flipSet.RowDelta, flipSet.ColDelta);
mBoard[pos.Row, pos.Col] = (sbyte)mCurrentPlayer;
Value += 2 * mCurrentPlayer;
Weight += 2 * mCurrentPlayer * mWeights[pos.Row, pos.Col];
}
}
// Check to see if the second-to-last move was a pass; if so, set PassCount.
if (MoveHistory.Count > 1 && (MoveHistory[MoveHistory.Count - 2] as OthelloMove).IsPass)
{
PassCount = 1;
}
}
else
{
PassCount--;
}
// Reset the remaining game state.
mCurrentPlayer = -mCurrentPlayer;
MoveHistory.RemoveAt(MoveHistory.Count - 1);
}
/// <summary>
/// Applies the given move to the board state.
/// </summary>
/// <param name="m">a move that is assumed to be valid</param>
public void ApplyMove(IGameMove move)
{
OthelloMove m = move as OthelloMove;
// If the move is a pass, then we do very little.
if (m.IsPass)
{
PassCount++;
}
else
{
PassCount = 0;
// Otherwise update the board at the move's position with the current player.
mBoard[m.Position.Row, m.Position.Col] = (sbyte)mCurrentPlayer;
Value += mCurrentPlayer;
// Iterate through all 8 directions radially from the move's position.
for (int rDelta = -1; rDelta <= 1; rDelta++)
{
for (int cDelta = -1; cDelta <= 1; cDelta++)
{
if (rDelta == 0 && cDelta == 0)
{
continue;
}
// Repeatedly move in the selected direction, as long as we find "enemy" squares.
BoardPosition newPos = m.Position;
int steps = 0;
do
{
newPos = newPos.Translate(rDelta, cDelta);
steps++;
} while (PositionInBounds(newPos) && PositionIsEnemy(newPos, mCurrentPlayer));
// This is a valid direction of flips if we moved at least 2 squares, and ended in bounds and on a
// "friendly" square.
if (steps > 1 && PositionInBounds(newPos) && mBoard[newPos.Row, newPos.Col] == mCurrentPlayer)
{
// Record this direction in the move's flipsets so the move can be undone.
m.AddFlipSet(
new OthelloMove.FlipSet()
{
RowDelta = rDelta,
ColDelta = cDelta,
Count = steps - 1
});
// The FlipSet constructor takes no parameters; this syntax allows us to construct a FlipSet
// and initialize many of its properties in one expression.
// Repeatedly walk back the way we came, updating the board with the current player's piece.
newPos = newPos.Translate(-rDelta, -cDelta);
while (steps > 1)
{
mBoard[newPos.Row, newPos.Col] = (sbyte)mCurrentPlayer;
Value += 2 * mCurrentPlayer;
newPos = newPos.Translate(-rDelta, -cDelta);
steps--;
}
}
}
}
}
// Update the rest of the board state.
mCurrentPlayer = -mCurrentPlayer;
MoveHistory.Add(m);
}
/// <summary>
/// Returns true if the two objects have the same position.
/// </summary>
public bool Equals(IGameMove obj)
{
OthelloMove other = obj as OthelloMove;
return(other.Position.Row == this.Position.Row && other.Position.Col == this.Position.Col);
}
