Randomly Choosing 10 out of 40

[Shamikh]

I need to be able to choose randomly 10 questions out of a possible 40:

code:

lol (1) := question1 lol (2) := question2 lol (3) := question3 lol (4) := question4 lol (5) := question5 lol (6) := question6 lol (7) := question7 lol (8) := question8 lol (9) := question9 lol (10) := question10 lol (11) := question11 lol (12) := question12 lol (13) := question13 lol (14) := question14 lol (15) := question15 lol (16) := question16 lol (17) := question17 lol (18) := question18 lol (19) := question19 lol (20) := question20 lol (21) := question21 lol (22) := question22 lol (23) := question23 lol (24) := question24 lol (26) := question26 lol (27) := question27 lol (28) := question28 lol (29) := question29 lol (30) := question30 lol (31) := question31 lol (32) := question32 lol (33) := question33 lol (34) := question34 lol (35) := question35 lol (36) := question36 lol (37) := question37 lol (38) := question38 lol (39) := question39 lol (40) := question40

lol is my array and the question1 etc.. are procedures. The only way i would do it is to somehow assign every question an int value and then randint, but i dont
know how. Some help plz.

code:

[Tony]

every question already has an int value -- the index of the array.

Also, randint is deprecated, use Rand.Int()

[Shamikh]

What do u mean the index of the array.
Sorry im so bad, im in grade 9 Compsci

[Shamikh]

understand the index but how do iput that into my randint equation?
p.s Rand.Int isnt working for me

[Tony]

Shamikh @ Mon Jun 02, 2008 7:29 pm wrote:

p.s Rand.Int isnt working for me

You're not doing it right.

Turing:

lol(Rand.Int(1,40))

Of course your next problem would be to make sure that you don't pick the same question twice. The usual approach is to have another array of indexes of elements that were not yet selected, and pick randomly from _that_ array.

[Shamikh]

So make another array from 1 to 40 then do the same thing with that? I dont quite understand.

[Shamikh]

So like this:
olo(lol(Rand.Int(1,40))

[Tony]

no, like over here

[Shamikh]

So i would make the following changes to this code to fit my program:

code:

var size:int :=10 var randN:int %just to hold the number var numbers:array 1..size of int for i:1..size numbers(i):=i end for for decreasing i:size ..1 randN := Rand.Int(1,i) put numbers(randN)     numbers(randN):=numbers(i) end for

Where would my lol go?

[Tony]

Once you figure out how that code snippet works, it should be rather obvious.

[Shamikh]

Still working on it, Remembr im Grade 9

[Shamikh]

It keeps saying lol has been previoulsy decalred

[Shamikh]

Someone Give me a hint.
Its Soooo Frustrating!

[richcash]

A hint? Well, lol is an array and I only see one array in that code snippet.

[Tony]

forget about lol for a moment. Start by explaining how that code gets to generate a random list.

protip: there's an explanation in the thread where you copied that code from.

Then figure out how to take numbers from that random list, one at a time.

Then we are back to

code:

lol(index)