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x2utils/X2UtTrees.pas

779 lines
18 KiB
ObjectPascal

{** Various tree implementations.
*
* Last changed: $Date$ <br />
* Revision: $Rev$ <br />
* Author: $Author$ <br />
}
unit X2UtTrees;
interface
uses
SysUtils;
type
EBTKeyExists = class(Exception);
EBTKeyNotFound = class(Exception);
EBTCursorEof = class(Exception);
EBTNoCursor = class(Exception);
{** Internal representation of a binary tree node.
*
* For the sake of easy lookups and cleaner code I chose to let nodes know
* who their parent is. It costs 4 bytes... but that's only 4 megabytes
* overhead for each million nodes, not much of a burden nowadays.
*}
TX2BTLinks = array[0..11] of Byte;
PX2BTNode = ^TX2BTNode;
TX2BTNode = record
Key: Cardinal;
case Boolean of
True:
(
Parent: PX2BTNode;
Left: PX2BTNode;
Right: PX2BTNode;
);
False:
(
Links: TX2BTLinks;
);
end;
{** Abstract cursor.
*
* Trees implement a descendant to traverse through the tree.
*}
TX2BTCustomCursor = class(TObject)
protected
function GetCurrentKey(): Cardinal; virtual; abstract;
function GetEof(): Boolean; virtual; abstract;
public
procedure First(); virtual; abstract;
procedure Next(); virtual; abstract;
property Eof: Boolean read GetEof;
property CurrentKey: Cardinal read GetCurrentKey;
end;
TX2BTCursorClass = class of TX2BTCustomCursor;
{** Default tree cursor.
*
* The default cursor traverses through the tree from top to bottom, left
* to right.
*}
TX2BTDefaultCursor = class(TX2BTCustomCursor)
private
FRoot: PX2BTNode;
FNode: PX2BTNode;
protected
function GetCurrentNode(): PX2BTNode;
function GetCurrentKey(): Cardinal; override;
function GetEof(): Boolean; override;
public
constructor Create(const ARoot: PX2BTNode); virtual;
procedure First(); override;
procedure Next(); override;
property CurrentNode: PX2BTNode read GetCurrentNode;
end;
{** Abstract tree manager.
*
* Trees implement a descendant to manage the tree nodes. This is where the
* actual tree is stored, and possibly optimized. All tree managers are
* assumed to store a 32-bit unsigned integer key with optional data.
*}
TX2BTCustomManager = class(TObject)
private
FCursor: TX2BTCustomCursor;
FDataSize: Cardinal;
protected
function GetCurrentKey(): Cardinal; virtual;
function GetEof(): Boolean; virtual;
procedure CursorNeeded(); virtual; abstract;
procedure InvalidateCursor(); virtual; abstract;
property Cursor: TX2BTCustomCursor read FCursor write FCursor;
public
constructor Create(); virtual;
destructor Destroy(); override;
procedure Clear(); virtual; abstract;
function Insert(const AKey: Cardinal): Boolean; virtual; abstract;
function Delete(const AKey: Cardinal): Boolean; virtual; abstract;
function Exists(const AKey: Cardinal): Boolean; virtual; abstract;
function GetData(const AKey: Cardinal): Pointer; virtual; abstract;
procedure First(); virtual;
procedure Next(); virtual;
property CurrentKey: Cardinal read GetCurrentKey;
property DataSize: Cardinal read FDataSize write FDataSize;
property Eof: Boolean read GetEof;
end;
TX2BTManagerClass = class of TX2BTCustomManager;
{** Default tree manager.
*}
TX2BTDefaultManager = class(TX2BTCustomManager)
private
FLastNode: PX2BTNode;
FRoot: PX2BTNode;
protected
procedure CursorNeeded(); override;
procedure InvalidateCursor(); override;
function FindLowestNode(const ANode: PX2BTNode): PX2BTNode;
function FindHighestNode(const ANode: PX2BTNode): PX2BTNode;
function FindNode(const AKey: Cardinal; out AParent: PX2BTNode): PX2BTNode;
function FindNodeOnly(const AKey: Cardinal): PX2BTNode;
function LeftChild(const ANode: PX2BTNode): Boolean;
function RightChild(const ANode: PX2BTNode): Boolean;
procedure SwapNodes(const ANode1, ANode2: PX2BTNode);
procedure DeleteCleanNode(var ANode: PX2BTNode); virtual;
procedure AllocateNode(var ANode: PX2BTNode); virtual;
procedure DeallocateNode(var ANode: PX2BTNode); virtual;
function GetNodeSize(): Cardinal; virtual;
public
procedure Clear(); override;
function Insert(const AKey: Cardinal): Boolean; override;
function Delete(const AKey: Cardinal): Boolean; override;
function Exists(const AKey: Cardinal): Boolean; override;
function GetData(const AKey: Cardinal): Pointer; override;
end;
{** Binary Tree implementation.
*
* Exposes the tree manager and handles node data.
*}
TX2BinaryTree = class(TObject)
private
FManager: TX2BTCustomManager;
function GetCurrentKey(): Cardinal;
function GetEof(): Boolean;
protected
function GetManagerClass(): TX2BTManagerClass; virtual;
public
constructor Create(); virtual;
destructor Destroy(); override;
{** Removes all nodes from the tree.
*}
procedure Clear();
{** Checks if a key already exists within the tree.
*
* @param AKey the key to search for
* @result True if the key exists, False otherwise
*}
function Exists(const AKey: Cardinal): Boolean;
{** Inserts a key into the tree.
*
* If a key already exists, an exception is raised.
*
* @param AKey the key for the new node
*}
procedure Insert(const AKey: Cardinal);
{** Deletes a key from the tree.
*
* If the key could not be found, an exception is raised.
*
* @param AKey the key to delete
*}
procedure Delete(const AKey: Cardinal);
{** Resets the cursor to the first node.
*
* Call First before iterating over all nodes. If no nodes are available,
* Eof will be set to True.
*}
procedure First();
{** Sets the cursor to the next node.
*
* Call Next while iterating over all nodes. If no more nodes are available,
* Eof will be set to True.
*}
procedure Next();
{** Returns the current key.
*
* Note: CurrentKey is only available when the cursor is valid.
*}
property CurrentKey: Cardinal read GetCurrentKey;
{** Determines if there are more nodes available.
*
* Read Eof before accessing CurrentKey to determine if the cursor is
* positioned at a valid node.
*}
property Eof: Boolean read GetEof;
end;
{** Binary Tree with integer data.
*
* Extends the standard Binary Tree, allowing it to store an Integer value
* for each node in the tree.
*}
TX2IntegerTree = class(TX2BinaryTree)
private
function GetItem(const AKey: Cardinal): Integer;
procedure SetItem(const AKey: Cardinal; const Value: Integer);
function GetCurrentValue: Integer;
public
constructor Create(); override;
property CurrentValue: Integer read GetCurrentValue;
property Items[const AKey: Cardinal]: Integer read GetItem
write SetItem; default;
end;
implementation
resourcestring
RSBTKeyExists = 'The key "%d" already exists in the tree.';
RSBTKeyNotFound = 'The key "%d" could not be found in the tree.';
RSBTCursorEof = 'Cursor is at Eof.';
RSBTNoCursor = 'Cursor not initialized, call First before Next.';
{===================== TX2BTDefaultCursor
Traversal
========================================}
constructor TX2BTDefaultCursor.Create;
begin
inherited Create();
FRoot := ARoot;
end;
procedure TX2BTDefaultCursor.First;
begin
FNode := FRoot;
end;
procedure TX2BTDefaultCursor.Next;
var
pChild: PX2BTNode;
begin
if Eof then
raise EBTCursorEof.Create(RSBTCursorEof);
if Assigned(FNode^.Left) then
// Node has a left child
FNode := FNode^.Left
else if Assigned(FNode^.Right) then
// Node has a right child
FNode := FNode^.Right
else
begin
// Traverse up the path. If we encounter a left direction, it means we
// can attempt to search the right part of that parent node.
repeat
pChild := FNode;
FNode := FNode^.Parent;
if Assigned(FNode) then
begin
if (FNode^.Left = pChild) and Assigned(FNode^.Right) then
begin
FNode := FNode^.Right;
break;
end;
end else
begin
FNode := nil;
break;
end;
until False;
end;
end;
function TX2BTDefaultCursor.GetCurrentNode;
begin
Result := FNode;
end;
function TX2BTDefaultCursor.GetCurrentKey;
begin
Result := CurrentNode^.Key;
end;
function TX2BTDefaultCursor.GetEof;
begin
Result := not Assigned(FNode);
end;
{===================== TX2BTCustomManager
Initialization
========================================}
constructor TX2BTCustomManager.Create;
begin
inherited;
end;
destructor TX2BTCustomManager.Destroy;
begin
Clear();
FreeAndNil(FCursor);
inherited;
end;
procedure TX2BTCustomManager.First;
begin
CursorNeeded();
FCursor.First();
end;
procedure TX2BTCustomManager.Next;
begin
CursorNeeded();
FCursor.Next();
end;
function TX2BTCustomManager.GetCurrentKey;
begin
if FCursor.Eof then
raise EBTCursorEof.Create(RSBTCursorEof);
Result := FCursor.CurrentKey;
end;
function TX2BTCustomManager.GetEof;
begin
Result := Assigned(FCursor) and (FCursor.Eof);
end;
{==================== TX2BTDefaultManager
Node Management
========================================}
procedure TX2BTDefaultManager.AllocateNode;
var
iSize: Cardinal;
begin
iSize := GetNodeSize() + FDataSize;
GetMem(ANode, iSize);
FillChar(ANode^, iSize, #0);
end;
procedure TX2BTDefaultManager.DeallocateNode;
begin
FreeMem(ANode, GetNodeSize() + FDataSize);
ANode := nil;
end;
function TX2BTDefaultManager.GetNodeSize;
begin
Result := SizeOf(TX2BTNode);
end;
procedure TX2BTDefaultManager.Clear;
var
pNode: PX2BTNode;
pParent: PX2BTNode;
begin
pNode := FRoot;;
while Assigned(pNode) do
begin
if Assigned(pNode^.Left) then
// Move down on the left side
pNode := pNode^.Left
else if Assigned(pNode^.Right) then
// Move down on the right side
pNode := pNode^.Right
else
begin
// Disconnect node from parent
pParent := pNode^.Parent;
if Assigned(pParent) then
if LeftChild(pNode) then
pParent^.Left := nil
else
pParent^.Right := nil;
DeallocateNode(pNode);
// Continue on the parent
if Assigned(pParent) then
pNode := pParent;
end;
end;
FLastNode := nil;
FRoot := nil;
end;
function TX2BTDefaultManager.FindHighestNode;
begin
Result := ANode;
while Assigned(Result) and Assigned(Result^.Right) do
Result := Result^.Right;
end;
function TX2BTDefaultManager.FindLowestNode;
begin
Result := ANode;
while Assigned(Result) and Assigned(Result^.Left) do
Result := Result^.Left;
end;
function TX2BTDefaultManager.FindNode;
var
pNode: PX2BTNode;
begin
// Quick check; was this node found previously
if Assigned(FLastNode) and (FLastNode^.Key = AKey) then
begin
Result := FLastNode;
exit;
end;
AParent := nil;
FLastNode := nil;
Result := nil;
pNode := FRoot;
while Assigned(pNode) do
if AKey = pNode^.Key then
begin
Result := pNode;
break;
end else
begin
AParent := pNode;
if AKey < pNode^.Key then
pNode := pNode^.Left
else
pNode := pNode^.Right;
end;
if Assigned(Result) then
FLastNode := Result;
end;
function TX2BTDefaultManager.FindNodeOnly;
var
pDummy: PX2BTNode;
begin
Result := FindNode(AKey, pDummy);
end;
function TX2BTDefaultManager.LeftChild;
begin
Assert(Assigned(ANode^.Parent), 'Node has no parent!');
Result := (ANode^.Parent^.Left = ANode);
end;
function TX2BTDefaultManager.RightChild;
begin
Result := not LeftChild(ANode);
end;
procedure TX2BTDefaultManager.SwapNodes;
procedure FixLinks(const ANode, AOld: PX2BTNode);
begin
if Assigned(ANode^.Parent) then
if ANode^.Parent^.Left = AOld then
ANode^.Parent^.Left := ANode
else
ANode^.Parent^.Right := ANode;
if Assigned(ANode^.Left) then
ANode^.Left^.Parent := ANode;
if Assigned(ANode^.Right) then
ANode^.Right^.Parent := ANode;
end;
var
pBuffer: TX2BTLinks;
begin
pBuffer := ANode1.Links;
ANode1.Links := ANode2.Links;
ANode2.Links := pBuffer;
FixLinks(ANode1, ANode2);
FixLinks(ANode2, ANode1);
if FRoot = ANode1 then
FRoot := ANode2
else if FRoot = ANode2 then
FRoot := ANode1;
end;
function TX2BTDefaultManager.Insert;
var
pNode: PX2BTNode;
pParent: PX2BTNode;
begin
Result := False;
pNode := FindNode(AKey, pParent);
if Assigned(pNode) then
exit;
Result := True;
InvalidateCursor();
AllocateNode(pNode);
FLastNode := pNode;
if not Assigned(FRoot) then
FRoot := pNode;
pNode^.Key := AKey;
if Assigned(pParent) then
begin
pNode^.Parent := pParent;
if AKey < pParent^.Key then
pParent^.Left := pNode
else
pParent^.Right := pNode;
end;
end;
function TX2BTDefaultManager.Delete;
var
pNode: PX2BTNode;
pLowest: PX2BTNode;
begin
Result := False;
pNode := FindNodeOnly(AKey);
if not Assigned(pNode) then
exit;
Result := True;
InvalidateCursor();
// If the node to be deleted has either one or no branch, it can simply be
// taken out of the chain. If it has two branches, find the lowest key on
// the right branch and swap it.
//
// Ex. delete 7 from the tree:
//
// 8 8
// 7 <-+ 4
// 2 5 | >>> 2 5
// 1 3 4 6 | 1 3 6
// +----+
if Assigned(pNode^.Left) and Assigned(pNode^.Right) then
begin
pLowest := FindLowestNode(pNode^.Right);
SwapNodes(pNode, pLowest);
end;
// At this point, the node is a leaf node or has only one branch
DeleteCleanNode(pNode);
end;
procedure TX2BTDefaultManager.DeleteCleanNode;
var
pParent: PX2BTNode;
pChild: PX2BTNode;
begin
pParent := ANode^.Parent;
// A 'clean' node is defined as a node with 0 or 1 child, which is easy
// to remove from the chain.
Assert(not (Assigned(ANode^.Left) and
Assigned(ANode^.Right)), 'Node is not a clean node!');
if Assigned(ANode^.Left) then
pChild := ANode^.Left
else
pChild := ANode^.Right;
// Link the parent to the new child
if Assigned(pParent) then
if LeftChild(ANode) then
pParent^.Left := pChild
else
pParent^.Right := pChild;
// Link the child to the new parent
if Assigned(pChild) then
pChild^.Parent := pParent;
if ANode = FRoot then
FRoot := pChild;
DeallocateNode(ANode);
end;
function TX2BTDefaultManager.Exists;
begin
Result := Assigned(FindNodeOnly(AKey));
end;
function TX2BTDefaultManager.GetData;
var
pNode: PX2BTNode;
begin
pNode := FindNodeOnly(AKey);
if not Assigned(pNode) then
raise EBTKeyNotFound.CreateFmt(RSBTKeyNotFound, [AKey]);
Result := Pointer(Cardinal(pNode) + GetNodeSize());
end;
procedure TX2BTDefaultManager.CursorNeeded;
begin
if not Assigned(FCursor) then
FCursor := TX2BTDefaultCursor.Create(FRoot);
end;
procedure TX2BTDefaultManager.InvalidateCursor;
begin
FreeAndNil(FCursor);
end;
{========================== TX2BinaryTree
Initialization
========================================}
constructor TX2BinaryTree.Create;
begin
inherited;
FManager := GetManagerClass().Create();
end;
destructor TX2BinaryTree.Destroy;
begin
FreeAndNil(FManager);
inherited;
end;
{========================== TX2BinaryTree
Interface
========================================}
procedure TX2BinaryTree.Clear;
begin
FManager.Clear();
end;
function TX2BinaryTree.Exists;
begin
Result := FManager.Exists(AKey);
end;
procedure TX2BinaryTree.Insert;
begin
if not FManager.Insert(AKey) then
raise EBTKeyExists.CreateFmt(RSBTKeyExists, [AKey]);
end;
procedure TX2BinaryTree.Delete;
begin
if not FManager.Delete(AKey) then
raise EBTKeyNotFound.CreateFmt(RSBTKeyNotFound, [AKey]);
end;
procedure TX2BinaryTree.First;
begin
FManager.First();
end;
procedure TX2BinaryTree.Next;
begin
FManager.Next();
end;
function TX2BinaryTree.GetManagerClass;
begin
Result := TX2BTDefaultManager;
end;
function TX2BinaryTree.GetCurrentKey;
begin
Result := FManager.CurrentKey;
end;
function TX2BinaryTree.GetEof;
begin
Result := FManager.Eof;
end;
{========================= TX2IntegerTree
Initialization
========================================}
constructor TX2IntegerTree.Create;
begin
inherited;
FManager.DataSize := SizeOf(Integer);
end;
function TX2IntegerTree.GetCurrentValue;
begin
Result := GetItem(FManager.CurrentKey);
end;
function TX2IntegerTree.GetItem;
begin
Result := PInteger(FManager.GetData(AKey))^;
end;
procedure TX2IntegerTree.SetItem;
begin
FManager.Insert(AKey);
PInteger(FManager.GetData(AKey))^ := Value;
end;
end.