1, Lua - rextester

1

local numbers, chars, infamies = {1, 5, 10, 50, 100, 500, 1000}, {"I", "V", "X", "L", "C", "D", "M"}, {}
local function ToRomanNumerals(input)
    input = math.floor(tonumber(input) or 0)
    if input <= 0 then return input end
    local result = ""
    for i = #numbers, 1, -1 do
        while input - numbers[i] >= 0 and input > 0 do
            result = result .. chars[i]
            input = input - numbers[i]
        end
        for j = 1, i - 1 do
            if input - (numbers[i] - numbers[j]) >= 0 and input < numbers[i] and input > 0 and numbers[i] - numbers[j] ~= numbers[j] then
                result = result .. chars[j] .. chars[i]
                input = input - (numbers[i] - numbers[j])
                break
            end
        end
    end
    return result
end
--GET 500 ROMAN NUMS
local longest = 0
for i = 0, 500, 1 do
    local num = ToRomanNumerals(i)
    if string.len(num) > longest then
        longest = string.len(num)
    end
    table.insert(infamies, {i, num, string.len(num)})
end
--SORT THEM BY ROMAN NUM LENGTH
table.sort(infamies, function(a, b) return a[3] < b[3] end)
--GROUP NUMS BY LENGTH
local groups = {}
for i=1,longest,1 do
    table.insert(groups,{})
end
for i, v in pairs(infamies) do
    table.insert(groups[v[3]],v)
end
--SORT EACH GROUP BY INFAMY NUMBER
for i, v in pairs(groups) do
    table.sort(groups[i], function(a, b) return a[1] < b[1] end)
end
--PRINT STUFF
for i, v in pairs(groups) do
    print("----------------------------------")
    for ii,vv in pairs(v) do
        print(vv[1], vv[2], vv[3])
    end
end


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