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September 7, 2018 00:22
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--sort core | |
-- | |
-- stable sorting routines for lua | |
-- | |
--based on MIT licensed code from Dirk Laurie and Steve Fisher | |
--license as follows: | |
--[[ | |
Copyright © 2013 Dirk Laurie and Steve Fisher. | |
Permission is hereby granted, free of charge, to any person obtaining a | |
copy of this software and associated documentation files (the "Software"), | |
to deal in the Software without restriction, including without limitation | |
the rights to use, copy, modify, merge, publish, distribute, sublicense, | |
and/or sell copies of the Software, and to permit persons to whom the | |
Software is furnished to do so, subject to the following conditions: | |
The above copyright notice and this permission notice shall be included in | |
all copies or substantial portions of the Software. | |
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING | |
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER | |
DEALINGS IN THE SOFTWARE. | |
]] | |
-- (modifications by Max Cahill 2018) | |
local _sort_core = {} | |
--tune | |
_sort_core.max_chunk_size = 24 | |
function _sort_core.insertion_sort_impl( array, first, last, less ) | |
for i = first + 1, last do | |
local k = first | |
local v = array[i] | |
for j = i, first + 1, -1 do | |
if less( v, array[j-1] ) then | |
array[j] = array[j-1] | |
else | |
k = j | |
break | |
end | |
end | |
array[k] = v | |
end | |
end | |
function _sort_core.merge( array, workspace, low, middle, high, less ) | |
local i, j, k | |
i = 1 | |
-- copy first half of array to auxiliary array | |
for j = low, middle do | |
workspace[ i ] = array[ j ] | |
i = i + 1 | |
end | |
-- sieve through | |
i = 1 | |
j = middle + 1 | |
k = low | |
while true do | |
if (k >= j) or (j > high) then | |
break | |
end | |
if less( array[ j ], workspace[ i ] ) then | |
array[ k ] = array[ j ] | |
j = j + 1 | |
else | |
array[ k ] = workspace[ i ] | |
i = i + 1 | |
end | |
k = k + 1 | |
end | |
-- copy back any remaining elements of first half | |
for k = k, j-1 do | |
array[ k ] = workspace[ i ] | |
i = i + 1 | |
end | |
end | |
function _sort_core.merge_sort_impl(array, workspace, low, high, less) | |
if high - low <= _sort_core.max_chunk_size then | |
_sort_core.insertion_sort_impl( array, low, high, less ) | |
else | |
local middle = math.floor((low + high)/2) | |
_sort_core.merge_sort_impl( array, workspace, low, middle, less ) | |
_sort_core.merge_sort_impl( array, workspace, middle + 1, high, less ) | |
_sort_core.merge( array, workspace, low, middle, high, less ) | |
end | |
end | |
--inline common setup stuff | |
function _sort_core.sort_setup(array, less) | |
local n = #array | |
local trivial = false | |
--trivial cases; empty or 1 element | |
if n <= 1 then | |
trivial = true | |
else | |
--default less | |
less = less or function (a, b) | |
return a < b | |
end | |
--check less | |
if less(array[1], array[1]) then | |
error("invalid order function for sorting") | |
end | |
end | |
--setup complete | |
return trivial, n, less | |
end | |
function _sort_core.stable_sort(array, less) | |
--setup | |
local trivial, n, less = _sort_core.sort_setup(array, less) | |
if not trivial then | |
--temp storage | |
local workspace = {} | |
workspace[ math.floor( (n+1)/2 ) ] = array[1] | |
--dive in | |
_sort_core.merge_sort_impl( array, workspace, 1, n, less ) | |
end | |
return array | |
end | |
function _sort_core.insertion_sort(array, less) | |
--setup | |
local trivial, n, less = _sort_core.sort_setup(array, less) | |
if not trivial then | |
_sort_core.insertion_sort_impl(array, 1, n, less) | |
end | |
return array | |
end | |
--export sort core | |
table.insertion_sort = _sort_core.insertion_sort | |
table.stable_sort = _sort_core.stable_sort | |
table.unstable_sort = table.sort |
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