private void AddSupplementaryMove(Move move, Pile pile, HoldingSet holdingSet, bool undoHolding)
        {
            // Add moves to the holding piles.
            for (int i = 0; i < holdingSet.Count; i++)
            {
                HoldingInfo holding     = holdingSet[i];
                Move        holdingMove = new Move(MoveType.Basic, MoveFlags.Holding, move.From, -holding.Length, holding.To);
                WorkingTableau.Move(holdingMove);
                SupplementaryMoves.Add(holdingMove);
            }

            // Add the primary move.
            WorkingTableau.UncheckedMove(new Move(move.From, move.FromRow, move.To));
            SupplementaryMoves.Add(move);

            if (undoHolding)
            {
                // Undo moves from the holding piles.
                for (int i = holdingSet.Count - 1; i >= 0; i--)
                {
                    HoldingInfo holding     = holdingSet[i];
                    Move        holdingMove = new Move(MoveType.Basic, MoveFlags.UndoHolding, holding.To, -holding.Length, move.To);
                    if (!WorkingTableau.TryMove(holdingMove))
                    {
                        break;
                    }
                    SupplementaryMoves.Add(holdingMove);
                }
            }
        }
        private void RestoreWorkingState()
        {
            // Restore state of the working tableau prior to intermediate move.
            WorkingTableau.Revert(tableauCheckPoint);

            // Restore state of supplementary moves prior to intermediate move.
            while (SupplementaryMoves.Count > supplementaryMovesCount)
            {
                SupplementaryMoves.RemoveAt(SupplementaryMoves.Count - 1);
            }
        }
        private void CheckOne(Move uncoveringMove)
        {
            // Prepare data structures.
            order = 0;
            int runs = Roots.Count - 1;

            Offload = OffloadInfo.Empty;
            SupplementaryMoves.Clear();

            // Initialize the pile map.
            WorkingTableau.Clear();
            WorkingTableau.CopyUpPiles(FindTableau);
            WorkingTableau.BlockDownPiles(FindTableau);

            if (!uncoveringMove.IsEmpty)
            {
                // Update the map for the uncovering move but don't
                // include its order contribution so we don't make
                // the uncovering move unless it is really necessary.
                MoveStack.Clear();
                for (int next = uncoveringMove.HoldingNext; next != -1; next = SupplementaryList[next].Next)
                {
                    Move holdingMove = SupplementaryList[next];
                    Move forwardMove = new Move(MoveType.Basic, MoveFlags.Holding, holdingMove.From, holdingMove.FromRow, holdingMove.To);
                    SupplementaryMoves.Add(forwardMove);
                    WorkingTableau.Move(forwardMove);
                    MoveStack.Push(new Move(MoveType.Basic, MoveFlags.UndoHolding, holdingMove.To, -holdingMove.ToRow, uncoveringMove.To));
                }
                SupplementaryMoves.Add(uncoveringMove);
                WorkingTableau.Move(uncoveringMove);
                while (MoveStack.Count > 0)
                {
                    Move holdingMove = MoveStack.Pop();
                    if (!WorkingTableau.IsValid(holdingMove))
                    {
                        break;
                    }
                    SupplementaryMoves.Add(holdingMove);
                    WorkingTableau.Move(holdingMove);
                }
            }

            // Check all the roots.
            int offloads = 0;

            for (int n = 1; n < Roots.Count; n++)
            {
                int  rootRow       = Roots[n];
                Card rootCard      = fromPile[rootRow];
                int  runLength     = Roots[n - 1] - Roots[n];
                int  suits         = fromPile.CountSuits(rootRow, rootRow + runLength);
                int  maxExtraSuits = ExtraSuits(GetNumberOfSpacesLeft());
                bool suitsMatch    = false;
                HoldingStack.Clear();

                // Try to find the best matching target.
                int to = -1;
                for (int i = 0; i < NumberOfPiles; i++)
                {
                    if (i == from)
                    {
                        continue;
                    }
                    Card card = WorkingTableau.GetCard(i);
                    if (card.IsTargetFor(rootCard))
                    {
                        if (!Offload.IsEmpty && to == Offload.To)
                        {
                            to         = -1;
                            suitsMatch = false;
                        }
                        if (!suitsMatch && card.Suit == rootCard.Suit)
                        {
                            to         = i;
                            suitsMatch = true;
                        }
                        else if (to == -1)
                        {
                            to = i;
                        }
                    }
                }

                MoveType type      = MoveType.Basic;
                bool     isOffload = false;
                if (to != -1)
                {
                    // Check for inverting.
                    if (!Offload.IsEmpty && to == Offload.To)
                    {
                        if (!Offload.SinglePile)
                        {
                            // Not enough spaces to invert.
                            return;
                        }
                    }

                    // Try to move this run.
                    if (suits - 1 > maxExtraSuits)
                    {
                        // Try using holding piles.
                        suits -= FindHolding(WorkingTableau, HoldingStack, false, fromPile, from, rootRow, rootRow + runLength, to, maxExtraSuits);
                        if (suits - 1 > maxExtraSuits)
                        {
                            // Not enough spaces.
                            return;
                        }
                    }

                    // Record the order improvement.
                    order += GetOrder(true, suitsMatch);
                }
                else
                {
                    if (!Offload.IsEmpty)
                    {
                        // Already have an offload.
                        return;
                    }

                    // It doesn't make sense to offload the last root.
                    if (rootRow == 0)
                    {
                        if (runs - 1 >= 2)
                        {
                            AddMove(order);
                        }
                        return;
                    }

                    // Check for partial offload.
                    if (offloads > 0)
                    {
                        AddMove(order);
                    }

                    // Try to offload this run.
                    if (GetNumberOfSpacesLeft() == 0)
                    {
                        // Not enough spaces.
                        return;
                    }
                    to = WorkingTableau.Spaces[0];
                    int maxExtraSuitsOnePile = ExtraSuits(GetNumberOfSpacesLeft() - 1) + 1;
                    if (suits > maxExtraSuitsOnePile)
                    {
                        // Try using holding piles.
                        suits -= FindHolding(WorkingTableau, HoldingStack, false, fromPile, from, rootRow, rootRow + runLength, to, maxExtraSuits);
                        if (suits > maxExtraSuits)
                        {
                            // Still not enough spaces.
                            return;
                        }
                    }
                    int numberOfSpacesUsed = SpacesUsed(GetNumberOfSpacesLeft(), suits);
                    Offload   = new OffloadInfo(to, numberOfSpacesUsed);
                    type      = Offload.SinglePile ? MoveType.Basic : MoveType.Unload;
                    isOffload = true;
                    offloads++;
                }

                // Do the move and the holding moves.
                HoldingSet holdingSet  = HoldingStack.Set;
                bool       undoHolding = !isOffload;
                AddSupplementaryMove(new Move(type, from, rootRow, to), fromPile, holdingSet, undoHolding);

                // Check whether the offload matches the new from or to piles.
                if (!isOffload)
                {
                    CheckOffload(to);
                }

                // Check whether any of the one run piles now match
                // the new from or to piles.
                for (int i = 0; i < OneRunPiles.Count; i++)
                {
                    if (CheckOneRun(to, OneRunPiles[i]))
                    {
                        // Found an emptying move.
                        return;
                    }
                }
            }

            // Check for unload that needs to be reloaded.
            if (!Offload.IsEmpty && !Offload.SinglePile)
            {
                if (FindTableau.GetDownCount(from) != 0)
                {
                    // Can't reload.
                    return;
                }
                else
                {
                    // Reload the offload onto the now empty space.
                    SupplementaryMoves.Add(new Move(MoveType.Reload, Offload.To, 0, from, 0));
                }
            }

            // Add the move.
            AddMove(order);
        }