Need help with random number generator

Anon

Let's say I want to generate a list of random numbers, chosen between 1 and 100, and I want to generate 20 of them and put them into an array. I can do the following:

srand(time());
for ($i = 0; $index < 20; $i++)
{
$rnum[$i] = (rand()%100)+1;
}

This may sound stupid, but I need to make sure that none of the numbers in the array are replicated, and I'm having a hard time. How do I go about doing this?

Thanks a million,

Jason.

Anon

Type: $index should be $i

Anon

Hey.

This codesnippet should solve your little problem.

<?
srand(time());
for ($i = 0; $i < 20; $i++)
{
$rnum[$i] = (rand()%100)+1;
$tmpvar = $rnum[$i];
for ($count = 0; $count < $i; $count ++)
{
if ($tmpvar == $rnum[$count])
{
$rnum[$count] = (rand()%100)+1;
$count = 0;
}
}
print "$rnum[$i]\n";
}
?>

What we do is check every random number with what is allredy in the array, and if there is a match we generate a new number and try again.

Anon

Sorry, the earlier posting does'nt seeme to work. After running it several times i found of it produced identical nrs. But i made a new one that i have tested without any identical nrs so far.......hope thisone works 😉

srand(time());

for ($i = 0; $i < 20; $i++)
{
$rnum[$i] = (rand()%100)+1;

for ($count = 0; $count < $i; $count ++)
{
if ($rnum[$i] == $rnum[$count])
{
$rnum[$i] = (rand()%100)+1;
$count = 0;

}
}

print "$rnum[$i]\n";
}

Anon

use in_array() instead of looping through the array each time.

Anon

Here's a real simple version using some of the nifty functions in the array section of the manual:

Make an array with all the numbers

from 1 to 100 in it:

$nums=range(1,100);

Now shuffle it:

shuffle ($nums);

now print out the first 20:

for ($count=0;$count<20;$count++){
print $nums[$count].'<BR>';
}

Anon

but when using the shuffle, can you then be 100% sure the array does'nt contain two identical numbers?? From what i can see all it does is randomize the order in the array.

Anon

Sure you can. The mathematical function of range creates an array, which contains numbers from the low to high limits passed to it. So, the first line of:

$nums=range(1,100);

makes an array that contains the numbers 1 through 100, in order, with no dups.

The shuffle command works by mixing array elements, no new elements are created, and none are duplicated during the shuffling process.

Anon

I dont know using ur syntax turn the program into infinite loop.

Thanx and regards
Avinash