Thread: Creating a random array

FAQ > How do I... (Level 1) > Generate random numbers?

I have the random array but I can't figure out how to make the numbers range from 1 to 1000.
here is the code.

Code:

#include<stdio.h>
#include<stdlib.h>

#define ARY_SIZE 500

int bldarray (int randN[]);
void printArray(int data[], int size);

int main(void)
{
  int randN[ARY_SIZE];
  int R;

  R = bldarray(randN);
  printArray(randN, ARY_SIZE);

  return(0);
}

int bldarray (int randN[])
{
  int i;
  int randNo;
  int h[ARY_SIZE] = {0};

  for(i = 0; i < ARY_SIZE; i++)
  {
    do
    {
      randNo = rand() % ARY_SIZE;
    }while (h[randNo] == 1);
    h[randNo] = 1;
    randN[i] = randNo;

  }
 return;
}


void printArray(int data[], int size)
{
  int i;
  int numP = 0;

  for(i = 0; i < size; i++)
  {
    numP++;
    printf("%d\n", data[i]);

  }
  return;
}

Can Anyone Help?

Try reading the whole FAQ entry that Dave pointed you to. There's a whole section that starts with "To generate numbers in a specific range, you have to use some simple maths."

First, you'll want this:

Code:

int main(void)
{
  int randN[ARY_SIZE];
  int R;
  srand(time(0));

And if you want a range of 1000, this will get you 0-999:

Code:

int bldarray (int randN[])
{
  int i;
  int randNo;
  int h[ARY_SIZE] = {0};

  for(i = 0; i < ARY_SIZE; i++)
  {
    do
    {
      randNo = rand() % 1000;
    }while (h[randNo] == 1);
    h[randNo] = 1;
    randN[i] = randNo;

  }
 return;
}

Fix the things your compiler warns you about, too.