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Copy pathMergeSort.lua
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58 lines (52 loc) · 1.62 KB
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-----------------------------------------------
-- [FILE] MergeSort.lua
-- [DATE] 2016-07-04
-- [CODE] BY gaofeng
-- [MARK] NONE
-----------------------------------------------
--[[
归并排序
合并两个已经排好序的数组，
设定两个指针， 最初位置分别为两个已经排好序的序列的起始位置。
比较破两个指针所指元素， 选择相对较小的元素， 放到合并后的数组，并移动指针
重复上一操作， 直到某一个指针到达数组尾部，
将另一序列剩下的所有元素直接复制到合并后的数组。
]]
local function merge(tmp, arr, low, mid, high, sortFunc)
for i=low, high do
tmp[i] = arr[i]
end
local li, ri = low, mid + 1
for i=low, high do
if li > mid then
arr[i] = tmp[ri]
ri = ri + 1
elseif ri > high then
arr[i] = tmp[li]
li = li + 1
elseif sortFunc(tmp[li], tmp[ri]) then
arr[i] = tmp[li]
li = li + 1
else
arr[i] = tmp[ri]
ri = ri + 1
end
end
end
local function _mergeSort(tmp, arr, low, high, sortFunc)
if low >= high then return end
local mid = math.floor((low + high) / 2)
_mergeSort(tmp, arr, low, mid, sortFunc)
_mergeSort(tmp, arr, mid + 1, high, sortFunc)
merge(tmp, arr, low, mid, high, sortFunc)
end
local defaultSortFunc = function (a, b)
return a < b
end
local function mergeSort(arr, sortFunc)
sortFunc = sortFunc or defaultSortFunc
local tmp = {}
local len = #arr
_mergeSort(tmp, arr, 1, len, sortFunc)
end
return mergeSort