%%%----------------------------------------------------------------------
%%% File : treap.erl
%%% Author : Alexey Shchepin <alexey@process-one.net>
%%% Purpose : Treaps implementation
%%% Created : 22 Apr 2008 by Alexey Shchepin <alexey@process-one.net>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2008 Process-one
%%%
%%% This program is free software; you can redistribute it and/or
%%% modify it under the terms of the GNU General Public License as
%%% published by the Free Software Foundation; either version 2 of the
%%% License, or (at your option) any later version.
%%%
%%% 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. See the GNU
%%% General Public License for more details.
%%%
%%% You should have received a copy of the GNU General Public License
%%% along with this program; if not, write to the Free Software
%%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
%%% 02111-1307 USA
%%%
%%%----------------------------------------------------------------------
-module(treap).
-export([empty/0,
insert/4,
delete/2,
delete_root/1,
get_root/1,
lookup/2,
is_empty/1]).
empty() ->
nil.
insert(Key, Priority, Value, Tree) ->
HashKey = {erlang:phash2(Key), Key},
insert1(Tree, HashKey, Priority, Value).
insert1(nil, HashKey, Priority, Value) ->
{HashKey, Priority, Value, nil, nil};
insert1({HashKey1, Priority1, Value1, Left, Right},
HashKey, Priority, Value) ->
if
HashKey < HashKey1 ->
heapify({HashKey1, Priority1, Value1,
insert1(Left, HashKey, Priority, Value),
Right});
HashKey > HashKey1 ->
heapify({HashKey1, Priority1, Value1,
Left,
insert1(Right, HashKey, Priority, Value)});
true ->
erlang:error(key_exists)
end.
heapify(nil) ->
nil;
heapify({_HashKey, _Priority, _Value, nil, nil} = Tree) ->
Tree;
heapify({HashKey, Priority, Value,
nil = Left,
{HashKeyR, PriorityR, ValueR, LeftR, RightR}} = Tree) ->
if
PriorityR > Priority ->
{HashKeyR, PriorityR, ValueR,
{HashKey, Priority, Value, Left, LeftR},
RightR};
true ->
Tree
end;
heapify({HashKey, Priority, Value,
{HashKeyL, PriorityL, ValueL, LeftL, RightL},
nil = Right} = Tree) ->
if
PriorityL > Priority ->
{HashKeyL, PriorityL, ValueL,
LeftL,
{HashKey, Priority, Value, RightL, Right}};
true ->
Tree
end;
heapify({HashKey, Priority, Value,
{HashKeyL, PriorityL, ValueL, LeftL, RightL} = Left,
{HashKeyR, PriorityR, ValueR, LeftR, RightR} = Right} = Tree) ->
if
PriorityR > Priority ->
{HashKeyR, PriorityR, ValueR,
{HashKey, Priority, Value, Left, LeftR},
RightR};
PriorityL > Priority ->
{HashKeyL, PriorityL, ValueL,
LeftL,
{HashKey, Priority, Value, RightL, Right}};
true ->
Tree
end.
delete(Key, Tree) ->
HashKey = {erlang:phash2(Key), Key},
delete1(HashKey, Tree).
delete1(HashKey, {HashKey1, Priority1, Value1, Left, Right} = Tree) ->
if
HashKey < HashKey1 ->
{HashKey1, Priority1, Value1, delete1(HashKey, Left), Right};
HashKey > HashKey1 ->
{HashKey1, Priority1, Value1, Left, delete1(HashKey, Right)};
true ->
delete_root(Tree)
end.
delete_root({HashKey, Priority, Value, Left, Right}) ->
case {Left, Right} of
{nil, nil} ->
nil;
{_, nil} ->
Left;
{nil, _} ->
Right;
{{HashKeyL, PriorityL, ValueL, LeftL, RightL},
{HashKeyR, PriorityR, ValueR, LeftR, RightR}} ->
if
PriorityL > PriorityR ->
{HashKeyL, PriorityL, ValueL,
LeftL,
delete_root({HashKey, Priority, Value, RightL, Right})};
true ->
{HashKeyR, PriorityR, ValueR,
delete_root({HashKey, Priority, Value, Left, LeftR}),
RightR}
end
end.
is_empty(nil) ->
true;
is_empty({_HashKey, _Priority, _Value, _Left, _Right}) ->
false.
get_root({{_Hash, Key}, Priority, Value, _Left, _Right}) ->
{Key, Priority, Value}.
lookup(Key, Tree) ->
HashKey = {erlang:phash2(Key), Key},
lookup1(Tree, HashKey).
lookup1(nil, _HashKey) ->
error;
lookup1({HashKey1, Priority1, Value1, Left, Right}, HashKey) ->
if
HashKey < HashKey1 ->
lookup1(Left, HashKey);
HashKey > HashKey1 ->
lookup1(Right, HashKey);
true ->
{ok, Priority1, Value1}
end.
