Even and Odd Numbers

filn

hey all. i need a little help. i want to separate out the even and odd numbers from a random number.

example:

say you have the number 10, i want to stick all the odd
numbers upto 10 into an array or something where i can give each one a value, and do the same for the even numbers.

heres another way of thinking of it: i want to take a random number and for all the even numbers upto that random number, i want to assign the value "right" and for all the odd numbers i want to be called "left." then i want to randomly choose from the "right" numbers and from the "left" numbers.

or think of it in the context of the whole script idea:

i want to make a script that takes a users input of a number, takes that number devides it by a random number. then it from that same number that was used to devide the user input and assigns the values of "left" and "right" to those.

ok this next part maybe a little confussing:

the ultimate output would look something like this:
(and for sake of simplicity im going to use the numbers 4000 as the user input and 4 as the random number.

-- start --

4000

1000
left
1000
left
1000
right
1000
right

--- end --

but in a more random kind of way. if anybody understands any of this, could you please offer some advice. thanks.

filn

this is just some follow up information:

if you could just tell me how to separate the even and odd numbers from 1 to 10 i think i can figure out the rest.

intenz

Try this...

for($i = 0; $i <= 10; $i++)
{
        if(($i % 2) != 0)
                $arrOdd[] = $i;
        else
                $arrEven[] = $i;
}
print_r($arrOdd);
echo '<br><br>';
print_r($arrEven);

james_holden

	function odd($num){
		return ($num % 2) ? 1 : 0;
	}

Weedpacket

Originally posted by james_holden
	function odd($num){
		return ($num % 2) ? 1 : 0;
	}
[/B]

Is equivalent to

	function odd($num){
		return ($num % 2);
	}

Or you could go

	function odd($num){
		return ($num & 1);
	}

if that takes your fancy.

filn

Originally posted by Weedpacket

Is equivalent to
	function odd($num){
		return ($num % 2);
	}
Or you could go
	function odd($num){
		return ($num & 1);
	}
if that takes your fancy. [/B]

do you think you could explain a little more. im no programmer 🙂

the_Igel

return ($num % 2);
returns the remainder of integer division of $num by 2. It is 0 in case of even $num and 1 in case of odd, and if interpreted as boolean - FALSE and TRUE respectively.

return ($num & 1);
& is logical AND. $num & 1 is the value of the first bit of $num. It is the same as the remainder of int.division by two.

On the other hand, here's the way to get random even or random odd number:

Say, you want to get random odd number 1 <= x <= 101
First, you obtain random integer 0 <= i <= 50, then multiply it by 2 and add 1.

filn

Originally posted by the_Igel
return ($num % 2);
returns the remainder of integer division of $num by 2. It is 0 in case of even $num and 1 in case of odd, and if interpreted as boolean - FALSE and TRUE respectively.

return ($num & 1);
& is logical AND. $num & 1 is the value of the first bit of $num. It is the same as the remainder of int.division by two.

ok ok, now bear with me here as i ask another question, how would i work the above into a loop to get all the even and odd numbers between X and Y ?

the_Igel

$odd = array();
$even = array();
$current_is_odd = X % 2;

for ($i = X; $i <= Y; $i++)
{
if ($current_is_odd) $odd[] = $i;
else $even[] = $i;
$current_is_odd = !$current_is_odd;
}

filn

Originally posted by the_Igel

$odd = array();
$even = array();
$current_is_odd = X % 2;

for ($i = X; $i <= Y; $i++)
{
if ($current_is_odd) $odd[] = $i;
else $even[] = $i;
$current_is_odd = !$current_is_odd;
}

[/B]

ok ok, now how do i use this to display, say just the odd numbers, or just the even numbers ?

the_Igel

You have now two arrays: $odd & $even.

Ex:
foreach($odd as $num)
echo $num.'<br>';