function factorial(n)
    for i = n-1, 2, -1 do
        n = n * i
    end
    return n
end

function permutar(text)
    local permut = {}
    local factorialLength = factorial(#text)
    local factorialLength1 = factorial(#text-1)

    if #text == 2 then
        local letterPos
        for i = 1, factorialLength do
            for j = 1, #text do
                letterPos = ((i+j) % #text) + 1
                permut[i] = (permut[i] or "")..text:sub(letterPos, letterPos)
            end
        end
    else
        for i = 1, factorialLength, factorialLength1 do
            local letterPos = math.floor((i/factorialLength1) % #text) + 1
            local letter = text:sub(letterPos, letterPos)
            for j = 1, factorialLength1 do
                permut[i+j-1] = (permut[i+j-1] or "")..letter
            end
            local nText = ""
            for j = 1, #text do
                if text:sub(j, j) ~= letter then
                    nText = nText..text:sub(j, j)
                end
            end
            local permut2 = permutar(nText)
            for j=1, #permut2 do
                permut[i+j-1] = (permut[i+j-1] or "")..(permut2[j] or "");
            end
        end
    end
    return permut
end

local text = "abc"
local permut = permutar(text)
for i=1, #permut do
    print(permut[i])
end
print(os.clock())