5 replies to this topic

[snorifu]

Hello,
I need to use the rand() function for my program. But it isn't working the way I want.
I think the code is now generating a number between the number choice[8] contains and a number choice[0] contains. But I want to get a number amongst these :1,2,3,5,6,7,8,9. Does anyone has a solution for this?
I'm not very good in English so please reply if you don't understand me.

int choice[8]={1,2,3,5,6,7,8,9};

srand(time (NULL));

number[0]=rand() % choice[8] + choice[0]; 

[notes]

i don't quite understand what you are trying to do, but you can randomize some int form 1-9 with:

yours_int = rand() % 9 + 1;

int choice[8];

is a 8 element table. To randomize it you shall use 'for' loop.
This is working for a windows.

#include <cstdlib>

#include <iostream>

#include <time.h>

using namespace std;


int main(int argc, char *argv[])

{

  int choice[8]; 

  srand ( time(NULL) );

  for (int i=0;i<8;i++)

   {choice[i]=  rand() % 9 + 1;

    cout <<endl << choice[i]; 

} 



    system("PAUSE");

    return EXIT_SUCCESS;

}

[Flying Dutchman]

some_random_number = rand() % lower_bound + upper_bound;

You can set ranges with that formula. So, if you'd want random numbers between [5, 15] then you'd say:

random_number = rand() % 11 + 5;

Since modulo operator ( % ) has higher precedence than addition, it will return a number between 0 and 10. Then'll add 5 and we get numbers in [5, 15] range.

[snorifu]

Thanks for your reply's but it's not what I mean.
I need to get a random numberout of an array. So the array could be {1,2,3,5,6,7,8,9}
but it could also be {1,4,7,2,9,6,5,4}. Now my question is is there a in built function in c++ or c that does that?

[WingedPanther]

You need to generate a random INDEX for the array, and then use that to access the element of interest, not generate it based on the values in fixed locations in the array.

[snorifu]

Thanks WingedPanther! That is exactly the solution I wanted:)
here is my code:

srand(time (NULL));

value=rand() % max + 0; 

number[0]=choice[value];

Edited by snorifu, 11 April 2011 - 12:45 AM.
forgot a semicolon