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{ Simple TRIE implementation.
Copyright (c) 2012 by Inoussa OUEDRAOGO
The source code is distributed under the Library GNU
General Public License with the following modification:
- object files and libraries linked into an application may be
distributed without source code.
If you didn't receive a copy of the file COPYING, contact:
Free Software Foundation
675 Mass Ave
Cambridge, MA 02139
USA
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. }
unit trie;
{$mode objfpc}{$H+}
interface
uses
SysUtils;
const
MAX_CHILD_COUNT = 256;
type
TKeyType = Cardinal;
TDataType = Integer;
PTrieNode = ^TTrieNode;
TTrieNode = packed record
Key : TKeyType;
DataNode : Boolean;
Data : TDataType;
ChildCount : Byte;
Children : array[0..(MAX_CHILD_COUNT-1)] of PTrieNode;
end;
function CreateNode(
const AKey : TKeyType;
const AData : TDataType
) : PTrieNode; overload;
function CreateNode(const AKey : TKeyType) : PTrieNode;overload;
procedure FreeNode(ANode : PTrieNode);
function InsertWord(
const ARoot : PTrieNode;
const AWord : array of TKeyType;
const AValue : TDataType
) : Boolean;overload;
function InsertWord(
const ARoot : PTrieNode;
const AWord : TKeyType;
const AValue : TDataType
) : Boolean;overload;
implementation
function CreateNode(
const AKey : TKeyType;
const AData : TDataType
) : PTrieNode;
begin
New(Result);
Result^.Key := AKey;
Result^.DataNode := True;
Result^.Data := AData;
Result^.ChildCount := 0;
end;
function CreateNode(const AKey : TKeyType) : PTrieNode;
begin
New(Result);
Result^.Key := AKey;
Result^.DataNode := False;
Result^.ChildCount := 0;
end;
procedure FreeNode(ANode : PTrieNode);
var
p : PTrieNode;
i : Integer;
begin
if (ANode = nil) then
exit;
p := ANode;
for i := 0 to p^.ChildCount - 1 do
FreeNode(p^.Children[i]);
Dispose(p);
end;
function InsertWord(
const ARoot : PTrieNode;
const AWord : TKeyType;
const AValue : TDataType
) : Boolean;
begin
Result := InsertWord(ARoot,[AWord],AValue);
end;
function InsertWord(
const ARoot : PTrieNode;
const AWord : array of TKeyType;
const AValue : TDataType
) : Boolean;
var
p : PTrieNode;
i, k, c : Integer;
searching : TKeyType;
found : Boolean;
begin
Result := False;
if (ARoot^.Key <> AWord[0]) then
exit;
p := ARoot;
i := 1;
c := Length(AWord);
while (i < c) do begin
searching := AWord[i];
found := False;
for k := 0 to p^.ChildCount - 1 do begin
if (p^.Children[k]^.Key = searching) then begin
p := p^.Children[k];
found := True;
Break;
end;
end;
if not found then
Break;
Inc(i);
end;
if (i < c) then begin
if (i = c) then
i := i - 1;
for i := i to c - 2 do begin
k := p^.ChildCount;
p^.Children[k] := CreateNode(AWord[i]);
p^.ChildCount := k + 1;
p := p^.Children[k];
end;
i := c - 1;
k := p^.ChildCount;
p^.Children[k] := CreateNode(AWord[i],AValue);
p^.ChildCount := k + 1;
Result := True;
end;
end;
end.
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