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linkedlists.lua
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linkedlists.lua
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-- Blind Tower Defense (temporal name)
-- Copyright 2009 Iwan Gabovitch, Christiaan Janssen, September 2009
--
-- This file is part of Blind Tower Defense
--
-- Blind Tower Defense 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 3 of the License, or
-- (at your option) any later version.
--
-- Blind Tower Defense 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 Blind Tower Defense If not, see <http://www.gnu.org/licenses/>.
-- Double Linked Lists
if not love then
require 'class'
end
List = class( function(list)
list.first = {next=nil, prev=nil, ref=nil, val=nil}
list.last = {next=nil, prev=nil, ref=nil, val=nil}
list.current = list.first
list.n = 0
end )
function List:discard()
local next = self.first.next
local elem = self.first
while elem do
elem.next = nil
elem.prev = nil
elem.ref = nil
elem.value = nil
elem = next
if elem then
next = elem.next
end
end
self.first = {next=nil, prev=nil, ref=nil, val=nil}
self.last = {next=nil, prev=nil, ref=nil, val=nil}
self.current = self.first
self.n = 0
end
-- push and pop functions
function List:pushFront(obj, value)
if not value then value=0 end
local new = { next = nil, prev = nil, ref = obj, val = value }
if self.n>0 then
self.first.prev = new
new.next = self.first
else
self.last = new
end
self.first = new
self.n = self.n + 1
end
function List:pushBack(obj, value)
if not value then value=0 end
local new = { next = nil, prev = nil, ref = obj, val = value }
if self.n>0 then
self.last.next = new
new.prev = self.last
else
self.first = new
end
self.last = new
self.n = self.n + 1
end
function List:popFront()
if self.n==0 then return nil end
local retval = self.first.ref
local newfirst = self.first.next
self.first.next = nil
if newfirst then
self.first = newfirst
newfirst.prev = nil
self.n = self.n - 1
else
self:discard()
end
return retval
end
function List:popBack()
if self.n==0 then return nil end
local retval = self.last.ref
local newlast = self.last.prev
self.last.prev = nil
if newlast then
self.last = newlast
newlast.next = nil
self.n = self.n - 1
else
self:discard()
end
return retval
end
-- read functions
function List:getFirst()
if self.n==0 then return nil end
self.current = self.first
return self.current.ref
end
function List:getNext()
if not self.current.next then return nil end
self.current = self.current.next
return self.current.ref
end
function List:getPrev()
if not self.current.prev then return nil end
self.current = self.current.prev
return self.current.ref
end
function List:getLast()
if self.n==0 then return nil end
self.current = self.last
return self.current.ref
end
function List:getCurrent()
return self.current.ref
end
-- remove current (use in combination with get*)
function List:removeCurrent()
if self.n == 0 then return end
if self.n == 1 then
self:discard()
return
end
if self.current.next and self.current.prev then
self.current.next.prev = self.current.prev
self.current.prev.next = self.current.next
--~ self.current = self.current.next
self.current.ref = nil
self.n = self.n - 1
return
end
-- first
if self.current == self.first then
self.first = self.first.next
self.first.prev = nil
self.current.next = nil
--~ self.current = self.first
self.current.ref = nil
self.n = self.n - 1
return
end
-- last
if self.current == self.last then
self.last = self.last.prev
self.last.next = nil
self.current.prev = nil
--~ self.current = self.last
self.current.ref = nil
self.n = self.n - 1
return
end
end
-- insert after current
function List:insert(obj, value)
if not value then value=0 end
if self.n<2 or self.current==self.last then
self:pushBack(obj,value)
return
end
local new = { next = self.current.next, prev = self.current, ref = obj, val = value }
self.current.next = new
new.next.prev = new
self.n = self.n + 1
end
--- sorting
function List:pushFrontSorted(obj, value)
if not value then value=0 end
if self.n==0 then
self:pushFront(obj,value)
return
end
if self.first.val > value then
self:pushFront(obj,value)
return
end
local elem = self:getFirst( list )
while elem and self.current.val < value do elem=self:getNext() end
if not elem then
self:pushBack(obj,value)
else
self:getPrev()
self:insert(obj,value)
end
end
function List:pushBackSorted(obj, value)
if not value then value=0 end
if self.n == 0 then
self:pushBack(obj,value)
return
end
if self.last.val < value then
self:pushBack(obj,value)
return
end
local elem = self:getLast( list )
while elem and self.current.val > value do elem=self:getPrev() end
if not elem then
self:pushFront(obj,value)
else
self:insert(obj,value)
end
end
-- changes the value of the current object and sorts again
function List:changeValue(value)
if not value then value=0 end
if self.current.val == value then return end
local savedref = self.current.ref
local oldval = self.current.val
local newval = value
local oldprev = self.current.prev
self:removeCurrent()
if newval>oldval then
-- move up
elem = self:getNext()
while elem and self.current.val < value do elem = self:getNext() end
if not elem then
self:pushBack(savedref,value)
else
self:getPrev()
self:insert(savedref,value)
end
else
-- move down
local elem = self:getPrev( list )
while elem and self.current.val > value do elem=self:getPrev() end
if not elem then
self:pushFront(savedref,value)
else
self:insert(savedref,value)
end
end
-- not sure about this...
self.current = oldprev
end
--~ -- Example of use (make the condition true to test)
if false then
list = List()
list:pushBack("abc")
list:pushBack("cde")
list:pushBack("def")
-- print
elem = list:getFirst()
while elem do
print(elem)
elem = list:getNext()
end
-- reset
print()
list:discard()
-- sort while inserting
list:pushFrontSorted("iii",3)
list:pushFrontSorted("ooo",4)
list:pushFrontSorted("aaa",1)
-- print in reverse order (from high to low)
elem = list:popBack()
while elem do
print(elem)
elem = list:popBack()
end
list:discard()
end