private bool TryAddOneRunMove(int oneRun, int target)
        {
            Pile oneRunPile = WorkingTableau[oneRun];

            if (oneRunPile.Count == 0)
            {
                return(false);
            }
            Card oneRunRootCard = oneRunPile[0];

            // Check whether the one run pile matches the target pile.
            Card targetCard = WorkingTableau.GetCard(target);

            if (!oneRunRootCard.IsSourceFor(targetCard))
            {
                return(false);
            }

            // Check whether we can make the move.
            int oneRunSuits         = oneRunPile.CountSuits();
            int oneRunMaxExtraSuits = ExtraSuits(GetNumberOfSpacesLeft());

            HoldingStack.Clear();
            if (oneRunSuits - 1 > oneRunMaxExtraSuits)
            {
                oneRunSuits -= FindHolding(WorkingTableau, HoldingStack, false, oneRunPile, oneRun, 0, oneRunPile.Count, target, oneRunMaxExtraSuits);
                if (oneRunSuits - 1 > oneRunMaxExtraSuits)
                {
                    // Not enough spaces and/or holding piles.
                    return(false);
                }
            }

            // Handle the messy cases.
            if (Offload.IsEmpty || Offload.SinglePile && FindTableau.GetDownCount(oneRun) == 0)
            {
                // Save working state.
                SaveWorkingState();

                // Found a home for the one run pile.
                AddSupplementaryMove(new Move(oneRun, 0, target), oneRunPile, HoldingStack.Set, true);

                if (AddMove(order + GetOrder(targetCard, oneRunRootCard)))
                {
                    return(true);
                }

                // Restore working state.
                RestoreWorkingState();
            }

            return(false);
        }
        private void CheckOffload(int to)
        {
            if (Offload.IsEmpty)
            {
                // No offload to check.
                return;
            }

            Pile offloadPile = WorkingTableau[Offload.To];

            if (offloadPile.Count == 0)
            {
                // A discard emptied the offload pile.
                Offload = OffloadInfo.Empty;
                return;
            }

            Card     offloadRootCard      = offloadPile[0];
            int      offloadSuits         = offloadPile.CountSuits();
            int      offloadMaxExtraSuits = ExtraSuits(GetNumberOfSpacesLeft());
            MoveType offloadType          = Offload.SinglePile ? MoveType.Basic : MoveType.Reload;

            // Check whether offload matches from pile.
            Card fromCard = WorkingTableau.GetCard(from);

            if (offloadRootCard.IsSourceFor(fromCard))
            {
                // Check whether we can make the move.
                bool canMove = true;
                HoldingStack.Clear();
                if (Offload.SinglePile && offloadSuits - 1 > offloadMaxExtraSuits)
                {
                    // Not enough spaces.
                    offloadSuits -= FindHolding(WorkingTableau, HoldingStack, false, offloadPile, Offload.To, 0, offloadPile.Count, from, offloadMaxExtraSuits);
                    if (offloadSuits - 1 > offloadMaxExtraSuits)
                    {
                        // Not enough spaces and/or holding piles.
                        canMove = false;
                    }
                }

                if (canMove)
                {
                    // Save working state.
                    SaveWorkingState();

                    // Offload matches from pile.
                    AddSupplementaryMove(new Move(offloadType, Offload.To, 0, from), offloadPile, HoldingStack.Set, true);

                    // Add the intermediate move.
                    AddMove(order + GetOrder(fromCard, offloadRootCard));

                    // Restore working state.
                    RestoreWorkingState();
                }
            }

            // Check whether offoad matches to pile.
            Card toCard = WorkingTableau.GetCard(to);

            if (offloadRootCard.IsSourceFor(toCard))
            {
                // Check whether we can make the move.
                bool canMove = true;
                HoldingStack.Clear();
                if (Offload.SinglePile && offloadSuits - 1 > offloadMaxExtraSuits)
                {
                    // Not enough spaces.
                    offloadSuits -= FindHolding(WorkingTableau, HoldingStack, false, offloadPile, Offload.To, 0, offloadPile.Count, to, offloadMaxExtraSuits);
                    if (offloadSuits - 1 > offloadMaxExtraSuits)
                    {
                        // Not enough spaces and/or holding piles.
                        canMove = false;
                    }
                }

                if (canMove)
                {
                    // Record the order improvement.
                    order += GetOrder(toCard, offloadRootCard);

                    // Found a home for the offload.
                    AddSupplementaryMove(new Move(offloadType, Offload.To, 0, to), offloadPile, HoldingStack.Set, true);

                    // Update the state.
                    Offload = OffloadInfo.Empty;
                }
            }
        }
        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);
        }