HELP!!! Random numbers and an array

python_4 · **Posted:** Mon Jan 12, 2004 6:29 pm

Hey guys, I need help with my project here. The problem is that I cannot make a program that will randomly select 9 numbers out of 1..20 and not select the selected numbers again. That is, i want help in creating a program which will select 9 DIFFERENT numbers from 1.. 20 and store it in different variables or an array, so that I can later use the array to call upon text files. That is, each number between 1..20 represents a text file. Please take into consideration that I must be able to use the numbers to call upon TEXT files. I would really really really appreciate if someone would help me out.

Tony · **Posted:** Mon Jan 12, 2004 6:33 pm

seems you're new, so I'll show you around a bit 8) There's this very interesting place on this forum called [Turing Source Code] The interesting thing is that it has a bunch of writen code that could have just what you're looking for Wink

such as this Random List Generator, check it out - it's just what you're looking for

McKenzie · **Posted:** Mon Jan 12, 2004 6:36 pm

So it sounds like you are making some trivia game and you want random catagories. You will need two arrays One to store your random picks and one to keep track of the spots you have used. Run a for loop from 1 to 9. Inside the for you must ensure that you randomly pick a unique number. What you need is a loop. You will keep looping until you randomly pick a number that has not been picked, then record that it has been picked.

python_4 · **Posted:** Mon Jan 12, 2004 6:42 pm

Thank you very much, that was exactly what i was looking for. I really appreciate for your help and time.

Tony · **Posted:** Mon Jan 12, 2004 9:52 pm

McKenzie wrote:

randomly pick a number that has not been picked

please stop curropting young programmers with false ways Laughing

I mean you're a teacher... shouldn't you like promote efficiency and correct programming approaches or something Thinking

McKenzie · **Posted:** Mon Jan 12, 2004 11:16 pm

yer kiddin right? Run your program and check the number of milliseconds, then run mine. Hmmm ... 190 vs 14 on my computer

code:

var now : int
var randN : int
var numbers : array 1 .. 10 of int
for i : 1 .. 10
numbers (i) := 1
end for

for i : 1 .. 10
loop
randN := Rand.Int (1, 10)
exit when numbers (randN) = 1
end loop
put randN
numbers (randN) := 0
end for
clock (now)
put now

Tony · **Posted:** Mon Jan 12, 2004 11:48 pm

try cloacking the programs with larger numbers. Seing as the running time is exponensial for yours and linear for mine... There got to be that magic number at which point my program gets more efficient Wink

McKenzie · **Posted:** Tue Jan 13, 2004 9:50 am

Oh you mean like:

code:

var now : int
var start : int
var randN : int
var n:int
var trialTimes : array 1 .. 5 of int
var arrSize : array 1 .. 5 of int := init (10, 100, 1000, 10000, 100000)
for trial : 1 .. 5
clock (start)
n:=arrSize(trial)
var numbers : array 1 .. n of int
for i : 1 .. n
numbers (i) := 1
end for
for i : 1 .. n
loop
randN := Rand.Int (1, n)
exit when numbers (randN) = 1
end loop
numbers (randN) := 0
end for
clock (now)
trialTimes (trial) := now - start
put trialTimes(trial)
end for
put "Trial":10,"size":10,"time":10,"time/n":10
for i : 1 .. 5
put i : 10,arrSize(i):10, trialTimes (i) : 5,trialTimes (i)/arrSize(i):10:1
end for

Run it, it's O(n)

McKenzie · **Posted:** Tue Jan 13, 2004 4:07 pm

Hey Tony,
I tried to time yours like mine, it kinda freezes.

Cervantes · **Posted:** Tue Jan 13, 2004 4:14 pm

go Mckenzie!! no.. go tony!!

*gives up and does the wave*

Tony · **Posted:** Tue Jan 13, 2004 4:18 pm

hahaha

well shit

In theory it is suppost to be faster since it's not exponensial algorythm... but I suppose variable declaration and array rearrangement slows it down enough Sad

I think we need to continue this discussion in another language that doesn't suck as much as turing Wink

Cervantes · **Posted:** Tue Jan 13, 2004 4:21 pm

*points at tony* BLASPHEMY!!!!

go Mckenzie!! go mckenzie!

McKenzie · **Posted:** Tue Jan 13, 2004 4:41 pm

Well, which one would you prefer?
QBASIC, Fortran, Pascal, Javascript, C, C++, Miranda, Prolog, simscript, Smalltalk, 8088 ASM, Visual Basic, GPSS, COBOL???

P.S. please don't pick COBOL (ouch)

Tony · **Posted:** Tue Jan 13, 2004 6:30 pm

haha

Java or C++ ofcourse 8)

python_4 · **Posted:** Tue Jan 13, 2004 7:07 pm

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