Thread: My C++ Homework...Simple Question

I need to draw 8 random numbers (from 1 to 4). The numbers can only repeat once. I need there to be two 1s, two 2s, two 3s, and two 4s in random order. I need them put into an array.

Example Output: 1,3,4,2,4,1,3,2 or 3,1,1,4,3,2,2,4 (I'm sure you get the idea!)

It would now equal:

Code:

intNumbers[8] = {1,3,4,2,4,1,3,2};

This is a small piece of a bigger project, so I not just on here asking for answers. I really need help with this one. I've been staring at the same 10 lines for several hours now.

Thanks in advance for any help!
Tin

If you have to use the C style array, random_shuffle will work with that also:

std::random_shuffle(intNumbers, intNumbers + 8);

Originally Posted by Daved

If you have to use the C style array, random_shuffle will work with that also:

std::random_shuffle(intNumbers, intNumbers + 8);

Darn it.

Thanks a million. Worked like a charm!

Just so you know, you need to use srand(time(0)) to seed rand(), which is used by random_shuffle(). Otherwise, you will get the exact same sequence every time you run your program--try it.

time() is in <ctime>

Luckily I already had that in my code. If I didn't, I would've been stumped. Thanks again!

Originally Posted by 7stud

Just so you know, you need to use srand(time(0)) to seed rand(), which is used by random_shuffle(). Otherwise, you will get the exact same sequence every time you run your program--try it.

The implementation of the STL that I use ( g++ ) dosen't make use of the normal rand(), srand() c-functions. It uses an internal random generator that cannot be seeded.
but it's simple to provide one if needed

Code:

struct randomgenerator {
   int operator()( int range ) {
       static int seeded = 0;
       if ( ! seeded ) {
           srand( time(0));
           ++seeded;
       }
       return rand() % range;
   }
};

use it this way:

Code:

    randomgenerator random;

    random_shuffle( intNumbers, intNumbers + 8, random );

Kurt

functor! Functor! I see you!

struct? <shudder>

Originally Posted by 7stud

functor! Functor! I see you!

struct? <shudder>

What's wrong with that struct. There is nothing to be hidden or protected ?
Kurt