/// <summary>
/// Undoes the last move, restoring the game to its state before the move was applied.
/// </summary>
public void UndoLastMove()
{
OthelloMove m = mMoveHistory.Last();
if (!m.IsPass)
{
// Reset the board at the move's position.
SetPlayerAtPosition(m.Position, 0);
mAdvantageValue += mCurrentPlayer;
BoardWeight += mCurrentPlayer * mPositionWeights[m.Position.Row, m.Position.Col];
// Iterate through the move's recorded flipsets.
foreach (var flipSet in mFlipSets.Last())
{
BoardPosition pos = m.Position;
// For each flipset, walk along the flipset's direction resetting pieces.
for (int i = 0; i < flipSet.Count; i++)
{
pos = pos.Translate(flipSet.Direction);
// At this moment, CurrentPlayer is actually the enemy of the move that
// we are undoing, whose pieces we must restore.
SetPlayerAtPosition(pos, CurrentPlayer);
mAdvantageValue += 2 * mCurrentPlayer;
BoardWeight += 2 * mCurrentPlayer * mPositionWeights[pos.Row, pos.Col];
}
}
// Check to see if the second-to-last move was a pass; if so, set PassCount.
if (mMoveHistory.Count > 1 && mMoveHistory[mMoveHistory.Count - 2].IsPass)
{
PassCount = 1;
}
}
else
{
PassCount--;
}
// Reset the remaining game state.
SetAdvantage();
mCurrentPlayer = -mCurrentPlayer;
mMoveHistory.RemoveAt(mMoveHistory.Count - 1);
mFlipSets.RemoveAt(mFlipSets.Count - 1);
}
public void ApplyMove(OthelloMove m)
{
if (m == null)
{
throw new ArgumentNullException(nameof(m));
}
List <FlipSet> currentFlips = new List <FlipSet>();
m.Player = CurrentPlayer;
// 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.
SetPlayerAtPosition(m.Position, CurrentPlayer);
mAdvantageValue += mCurrentPlayer;
// Iterate through all 8 directions radially from the move's position.
foreach (BoardDirection dir in BoardDirection.CardinalDirections)
{
// Repeatedly move in the selected direction, as long as we find "enemy" squares.
BoardPosition newPos = m.Position;
int steps = 0;
do
{
newPos = newPos.Translate(dir);
steps++;
} while (PositionIsEnemy(newPos, CurrentPlayer));
// 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 && GetPlayerAtPosition(newPos) == CurrentPlayer)
{
// Record a FlipSet for this direction
currentFlips.Add(new FlipSet(dir, (sbyte)(steps - 1)));
var reverse = -dir;
// Repeatedly walk back the way we came, updating the board with the current player's piece.
do
{
newPos = newPos.Translate(reverse);
SetPlayerAtPosition(newPos, CurrentPlayer);
mAdvantageValue += 2 * mCurrentPlayer;
steps--;
}while (steps > 1);
}
}
}
// Update the rest of the board state.
mCurrentPlayer = -mCurrentPlayer;
SetAdvantage();
mMoveHistory.Add(m);
mFlipSets.Add(currentFlips);
}
