Random # Generator.

**GrafixFairy** · 03-05-2014

I wrote a random number generator code (25 #'s between 0 & 99)and now i need to list odds and evens separately but i dont quite know how. I know if %2==0 means even else odd but i dont know how to write it here...output should look like:

ODD: 21 21 87 39 45 7 75 71 87 9 81 27 57
EVEN: 26 64 2 74 0 40 84 0 82 0 32 90

Can someone assist me with this please.

Code:

#include <cstdlib>
#include <iostream>
#include <ctime>


using namespace std;


int main()
{
    int x = 0;
    
    srand(time(0));
    
        for (int x = 1; x < 26; x++)
        cout << 0+(rand()%100) << endl;
 
    system("PAUSE");
    return 0;
}

**laserlight** · 03-05-2014

One option is to create two std::vector<int> containers: one to store the even numbers and the other to store the odd numbers. After you are done generating the numbers, loop over the respective vectors and print the contents.

**GrafixFairy** · 03-05-2014

someone suggested : You are generating the random number and immediately passing it to the screen without first storing it in a variable. First store the generated number in a variable and manipulate that variable as you see fit. Only then output the variable to the screen.

I tried but no success..im new to this so its really confusing

**GrafixFairy** · 03-05-2014

I wrtoe (below) Its crap but i tried

Code:

       for (int x = 1; x < 26; x++)
        cout << 1+(rand()%99) << endl;
 
 int Even = rand (); 
 int Odd = rand ();
 
 if ((Even % 2) ==0) 
{   
    cout << "EVEN: " << Even << endl;
}   
 if ((Odd % 2)==1)
 {
    cout << "ODD:" << Odd << endl;
}   
    system("PAUSE");
    return 0;
}

**laserlight** · 03-05-2014

Have you learnt about arrays and/or vectors, or other containers?

**Mario F.** · 03-05-2014

You are getting there.

- First, generate a number and store it inside a variable.
- Next, test that variable for odd or even.
- Finally output to screen according to the result of your test

**laserlight** · 03-05-2014

Well, if you're willing to "cheat", you can generate the odd numbers first and then the even numbers.

**GrafixFairy** · 03-05-2014

@lazerlight I learnt about arrays, thats as far as we are at school right now, but in a lecture class of a million and one not everyone is bound to catch on quick...@Mario F. i going to try that now

**laserlight** · 03-05-2014

Originally Posted by GrafixFairy

I learnt about arrays, thats as far as we are at school right now

Ah, then it is a good bet that you are expected to use them in this exercise. My suggestion in post #2 can be used with arrays too.

**Mario F.** · 03-05-2014

Originally Posted by GrafixFairy

@Mario F. i going to try that now

Once you do that you should have a better grasp of how you should store a value if you need to properly manipulate it. This is just an initial requirement because I detected you had trouble understanding a basic principle in programming that you are required to store values if you need to manipulate them.

You should then look to laserlight advise. In order to output the random numbers as you initially said, you will need those arrays (or vectors). In here the process will be similar to what you already learned:

- First, generate a number and store it inside a variable.
- Next, test that variable for odd or even.
- Next, add the variable value to the proper array (odd array or even array)
- Finally, output the arrays

**GrafixFairy** · 03-05-2014

2D or should i create two separate arrays? which is easier

**Mario F.** · 03-05-2014

I would go for two separate arrays. A 2D array would work, if you know how to handle it. But a 2D array doesn't really represent the idea of two sets of numbers (one odd and one even). It better suited for tabular data. In programming, an important concept you should take early on is that your data types should reflect your data also in purpose and semantics. Later on, as you become more and more comfortable with programming, you will find yourself breaking this "rule" on a regular basis. But by then you will have a better feeling when it makes sense to do so, or to stick to better suited data types.

**GrafixFairy** · 03-05-2014

Laserlight and Mario F. thanks alot for the help, i wrote it all down but i'll need to speak to my teacher tomorrow and find out what he requires us to use because i dont want a replay of last week when i created 2 diff arrays and when i handed it in he said i should have used 2D so he gave me and the whole class 0 (like i read minds kmt) . So again thank you thank you.

Better teachers than the one im stuck with for sure!

**jocdrew21** · 03-05-2014

Check this out. It has some good information when creating random numbers. You are using the C way, which is fine but C++ has a whole library for this.
<random> - C++ Reference

**Elysia** · 03-05-2014

Originally Posted by jocdrew21

Check this out. It has some good information when creating random numbers. You are using the C way, which is fine but C++ has a whole library for this.
<random> - C++ Reference

While normally I would agree with you, it seems that GrafixFairy is stuck on more basic principles for now that needs to be learnt first and has an idiot teacher, to boot. From what I heard, it wouldn't surprise me if GrafixFairy got a 0 for using the C++ random facilities rather than the C ones.
Still, it is good to know they exist, even if they aren't going to be used in the assignments.

Thread: Random # Generator.

Thread Tools

Search Thread

Display

Random # Generator.

Similar Threads

need a random number generator thats not compleatly random

Random Generator

Random generator 0 1

looking for a random # generator

Random Name Generator

Tags for this Thread