Unique Random Numbers

[pjw1607]

Right,

I require some code to have a final array of 5 random, yet unique (to each other), values.

In my code I have set up an array and a loop to insert random numbers (between a $min and a $max value) into it. This doesn't ensure that the numbers in the array are unique however.

If comparison of the numbers found that 2 or more were the same, I could simply generate another array of random numbers and keep doing this until it is ok. This however, could be endless.

Does anyone know of a good method of putting 5 random, yet unique numbers (between $min and $max) into an array?

Hope someone can help. I guess it's more a case of an algorithm rather than coding, but I would be grateful for some help.

Incidentally, the purpose is to randomly pick 5 different random records from a large record set, to display in a site.

Cheers,

Paul

[jayant]

Originally posted by pjw1607
If comparison of the numbers found that 2 or more were the same, I could simply generate another array of random numbers and keep doing this until it is ok. This however, could be endless.

Why geenrate whole array again. just genererate another number.

Do this:
Make a function that takes an array and a number as a argument.

Algo: When you insert the 'X'th number, check that all the 'X-1' numbers are different than it. If different then insert.

You return 0 from function in all cases except when array is full.
then you return 1.

function do_it(&$arr, $num) {
    $flag=0;
    for($i=0;$i<count($arr);$i++) {
        if($num==$arr[$i]) { $flag = 1; break; }
    }
    if($flag == 0) $arr[$i]=$num;
    if(count($arr)==5) return 1;
    else return 0;
}

//first initialize the seed for randomn number generator
srand(time());

// now call the function like this:
while(!do_it($arr,rand())) { ; }

[Weedpacket]

This has come up a couple of times before on this forum.