Lua基数排序：按位分桶的逐轮收集

table.sort(levels)                  -- 比较排序下限nlogn

local function radix(levels)
    local buckets = {}
    for _ = 1, 10 do buckets[#buckets + 1] = {} end
    local cur, div = levels, 1
    for _ = 1, 3 do             -- 3位数排3轮
        for _, v in ipairs(cur) do
            local d = math.floor(v / div) % 10
            table.insert(buckets[d + 1], v)
        end
        cur = {}
        for _, b in ipairs(buckets) do
            for _, v in ipairs(b) do
                cur[#cur + 1] = v   -- 按桶序收回
            end
        end
        for i = 1, 10 do buckets[i] = {} end
        div = div * 10
    end
    return cur
end
local sorted = radix({32, 5, 217, 90})
sendmsg(actor, 1, "排序尾值 " .. sorted[#sorted])