FrequencySort.lua

local function generateInput()
	local file = io.open("Input.txt", "w")

	local nums = {}

	for _ = 1, 100 do
		table.insert(nums, math.random(1, 100))
	end

	file:write(table.concat(nums, " "))

	file:close()
end
generateInput()

local function generateOutput()
	local inFile = io.open("Input.txt", "r")
	local input = inFile:read("*all")
	inFile:close()

	local unsorted = {}
	local function getInput()
		for num in string.gmatch(input, "%-?%d+") do
			table.insert(unsorted, tonumber(num))
		end
	end
	getInput()

	local cache = {}
	local function countDuplicates()
		for _, num in ipairs(unsorted) do
			if not cache[num] then
				cache[num] = 1
			else
				cache[num] = cache[num] + 1
			end
		end
	end
	countDuplicates()

	local sorted = {}
	local function sortDuplicates()
		local counts = {}
		for num, count in pairs(cache) do
			if counts[count] then
				table.insert(counts[count], num)
			else
				counts[count] = { num }
			end
		end

		for _, nums in ipairs(counts) do
			table.sort(nums)
		end

		for count, nums in ipairs(counts) do
			for _, num in ipairs(nums) do
				for _ = 1, count do
					table.insert(sorted, num)
				end
			end
		end
	end
	sortDuplicates()

	local outFile = io.open("Output.txt", "w")
	outFile:write(table.concat(sorted, " "))
	outFile:close()
end
generateOutput()