Generate random number without repetition

yubaro · January 2015

Hi, I have not been able to solve this problem, can anyone help me?

Can anyone help me with the code in lua? I found examples only in java.

Thanks

ar2rsawseen · January 2015

@yubaro I suppose you might have a limit on numbers to generate, like from 1 to 100

then what you can do is to create a table with values from 1 to 100, then get random table element and remove it from table, then again take random element from table, etc.

yubaro · January 2015

Thanks Arturs, you suggest me to do it with an enterFrame event?

pie · January 2015

@yubaro I'm sorry I am not sure what do you mean by repetition

you can use math.random and math.randomseed, getting your seed from os.timer() so that it's different on every app start.

math.randomseed(os.timer()) 
print(math.random())

if instead repetition is about the risk to get the same number again inside a loop, like in

for i=1,20 do 
 number = math.random(1,8)
end

I think you should "save" every number you get in a table, and then manually check if it already exists and act by consequence.

EDIT: ar2sawseen was faster, and maybe had a better solution

amin13a · January 2015

local rnd = {}
for i = 1, 100 do
rnd[i] = i
end
for i = 1, 100 do
local rand = math.random(1,100)
local tmp = rnd[i]
rnd[i] = rnd[rand]
rnd[rand] = tmp
end
Now You have a random table: rnd

yubaro · January 2015

thanks @pie, yes, not get the same number again inside a loop...you suggest me to do it with an enterFrame event?

pie · January 2015

@yubaro It really depends on what you need and your "big scheme": I would try to avoid onEnterFrame event since it's time based and happens continuously; but I could be wrong..

in some situations it's the only way.

I would do this:
if you just need it to get all numbers once, use a for
if you need to get a new number every now and then, use a function that does everything and call it only when it's needed
if you need a continuous number generation use onEnterFrame. Just keep in mind that it is casted on every frame (30 or 60 times per second - according to your project settings).
You could also use Timer class if you need more control.

good luck

yubaro · January 2015

I want my output something like:

local rand = math.random(1,10)
....
--code--
....
print(rand)

output random:
5
10
4
9
5..this not, other number
6
4
5..this not, other number
5..this not, other number
1
1..this not, other number
2
3
8
7

SinisterSoft · January 2015

Create a table, generate a random number, if the table entry[the random number]==nil then table entry[the random number]=true else generate another random number until done.

It will get slower and slower as the list gets filled up. You could pregenerate the list.

yubaro · January 2015

My problem is I can not solve as generate another random number, until find a different one to that already obtained:

Something, output random:
5
10
4
9
5..this not, other number
6
4
5..this not, other number
5..this not, other number
1
1..this not, other number
2
3
8
7

pie · January 2015

if you need to random sort a table I would do as @ar2sawseen suggested:
this, of course, assuming that I understood your needs

 
--create a table
local tmpTable = {} 
for i=1,10 do 
table.insert(tmpTable, i) --insert possible outcome numbers inside the table: at this time the table looks like tmpTable = {1,2,3,...10}
end
 
local function getNum()
	--get a random index from tmpTable
	local index = math.random(#tmpTable)
	--save the value of the number at given index
	local num = tmpTable[index]
	--remove index value (table.remove removes the value mantaining index integrity - which is needed to use # - lenght operator)
	table.remove(tmpTable, index)
	--return the number
	return num
end
 
--get your numbers/ your table randomly sorted
for q=1, 10 do
local number = getNum()
print(number)
end

yubaro · January 2015

Thanks @pie, is perfect

thanks all!

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