'Random' Question

Hi,

I am wondering if you can ,after making a random number, take away that number from the random generator so you won't get it again the next time you make a random number. I am using srand.

For example: x=rand()%10+1 //say for example this makes x = 3

when I do this again I want it to not make another 3.

Thank you in advance!

Last edited on

Zaita (1562)

Not in the way you are thinking.

But lets say you wanted to draw a lottery, numbers 1-10. Each number can only appear once. You'd do.

1 2 3 4 5 6 7 8 9 10 11 12 13

  vector<int> vBallList;

  for (int i = 0; i < 10; ++i)
   vBallList.push_back( (i+1) ); // numbers 1-10.

  srand(time(NULL));

  for (int i = 0; i < 10; ++i) {
   int no = rand() % (10-i);
   cout << "Number was: " << vBallList[no] << endl;
   // Remove Picked Number
   vBallList.erase (vBallList.begin()+no);
  }

Haven't tested, or compiled that code. So take is as pseudo-code. Thats the theory of how I'd do it.

Edit: Whoa. It worked first time lol. Scary

Last edited on

BlahBlah (7)

It worked!

Thank you, Zaita!

This also taught me what vectors were and how to use them.

Zaita (1562)

No worries :)
Vectors are good to know, just good C++ STL if you wanna learn them better.

BlahBlah (7)

Yeah, I was trying to do it with an array (which I eventually got it to work) ,but using vectors was so much easier.

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