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avglvltree: simplified delete

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git-svn-id: trunk@36140 -
This commit is contained in:
mattias 2012-03-17 21:33:12 +00:00
parent 23abaf2eae
commit 5102efbb95
1 changed files with 56 additions and 95 deletions
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97
components/lazutils/avglvltree.pas
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@ -1083,79 +1083,13 @@ var
OldParent, OldLeft, OldRight, Successor, OldSuccParent, OldSuccLeft, OldParent, OldLeft, OldRight, Successor, OldSuccParent, OldSuccLeft,
OldSuccRight: TAvgLvlTreeNode; OldSuccRight: TAvgLvlTreeNode;
OldBalance: integer; OldBalance: integer;
Child: TAvgLvlTreeNode;
begin begin
OldParent:=ANode.Parent; OldParent:=ANode.Parent;
OldBalance:=ANode.Balance; OldBalance:=ANode.Balance;
ANode.Parent:=nil; ANode.Parent:=nil;
ANode.Balance:=0; ANode.Balance:=0;
if ((ANode.Left=nil) and (ANode.Right=nil)) then begin if (ANode.Left<>nil) and (ANode.Right<>nil) then begin
// Node is Leaf (no children)
if (OldParent<>nil) then begin
// Node has parent
if (OldParent.Left=ANode) then begin
// Node is left child of OldParent
OldParent.Left:=nil;
Inc(OldParent.Balance);
end else begin
// Node is right child of OldParent
OldParent.Right:=nil;
Dec(OldParent.Balance);
end;
BalanceAfterDelete(OldParent);
end else begin
// Node is the only node of tree
fRoot:=nil;
end;
dec(FCount);
ANode.Free;
exit;
end;
if (ANode.Right=nil) then begin
// Left is only child
// and because DelNode is AVL, Right has no childrens
// replace DelNode with Left
OldLeft:=ANode.Left;
ANode.Left:=nil;
OldLeft.Parent:=OldParent;
if (OldParent<>nil) then begin
if (OldParent.Left=ANode) then begin
OldParent.Left:=OldLeft;
Inc(OldParent.Balance);
end else begin
OldParent.Right:=OldLeft;
Dec(OldParent.Balance);
end;
BalanceAfterDelete(OldParent);
end else begin
fRoot:=OldLeft;
end;
dec(FCount);
ANode.Free;
exit;
end;
if (ANode.Left=nil) then begin
// Right is only child
// and because DelNode is AVL, Left has no childrens
// replace DelNode with Right
OldRight:=ANode.Right;
ANode.Right:=nil;
OldRight.Parent:=OldParent;
if (OldParent<>nil) then begin
if (OldParent.Left=ANode) then begin
OldParent.Left:=OldRight;
Inc(OldParent.Balance);
end else begin
OldParent.Right:=OldRight;
Dec(OldParent.Balance);
end;
BalanceAfterDelete(OldParent);
end else begin
fRoot:=OldRight;
end;
dec(FCount);
ANode.Free;
exit;
end;
// DelNode has both: Left and Right // DelNode has both: Left and Right
// Replace ANode with symmetric Successor // Replace ANode with symmetric Successor
Successor:=ANode.FindSuccessor; Successor:=ANode.FindSuccessor;
@ -1199,6 +1133,33 @@ begin
fRoot:=Successor; fRoot:=Successor;
// delete Node as usual // delete Node as usual
Delete(ANode); Delete(ANode);
end else begin
// left or right is nil
if ANode.Left<>nil then
Child:=ANode.Left
else
Child:=ANode.Right;
if Child<>nil then
Child.Parent:=OldParent;
if (OldParent<>nil) then begin
// Node has parent
if (OldParent.Left=ANode) then begin
// Node is left child of OldParent
OldParent.Left:=Child;
Inc(OldParent.Balance);
end else begin
// Node is right child of OldParent
OldParent.Right:=Child;
Dec(OldParent.Balance);
end;
BalanceAfterDelete(OldParent);
end else begin
// Node is the only node of tree
fRoot:=Child;
end;
dec(FCount);
ANode.Free;
end;
end; end;
procedure TAvgLvlTree.Remove(Data: Pointer); procedure TAvgLvlTree.Remove(Data: Pointer);