The most inventive way to switch 2 values

Wildhoney · 01-04-2008, 04:13 PM

OK! A little game for you all

The only objective is to switch the values of $a and $b. The values of $a and $b are 1 and 2, respectively:

php Code:

$a = 1;
$b = 2;

So for example this is an easy way to do it:

php Code:

$c = $a;
$a = $b;
$b = $c;

However! We're not looking for the simplest way to do it, or the fastest, but rather, the most inventive way to do it! There are a couple of rules and those are:

eval and create_function functions are disallowed.
8 lines maximum but lines with only { and } on do not count towards that total. This does not include the 2 initial assignments of $a and $b, or any echoes of the values $a or $b.
You must have only one semi-colon per line (;) unless of course it's used elsewhere apart from indicating the end of a line. Thus you're not allowed to fuse 2 lines together into 1. The exception is a for loop to where you're allowed 2.

So basically $a must equal 2 and $b must equal 1 at the end of your code.

I'll start us off:

php Code:

list($a, $b) = str_split(strrev($a . $b), 1);

var_dump($a);
var_dump($b);

Put that mind to work! Oh, and just for Karl, you can't just set $a to 2 and $b to 1

You have to reference the first 2 variables set!

sjaq · 01-04-2008, 06:50 PM

PHP Code:


			
<?php 

    $a = 1;
    $b = 2;
    
    // just the simplest way...
    list($a, $b) = array($b, $a);
    
    var_dump($a);
    var_dump($b);

    $c = 1;
    $d = 2;
    
    list($c, $d) = array_reverse(array($c, $d));
    
    var_dump($c);
    var_dump($d);

    $e = 1;
    $f = 2;
    
    $vars = array('e' => $e, 'f' => $f);
    extract(array_combine(array_reverse(array_keys($vars)), array_values($vars)));
    
    var_dump($e);
    var_dump($f);

?>

Not that innovative but wanted to give it a try..

Wildhoney · 01-04-2008, 07:12 PM

Lol at the last one

Very confusing!

Alan @ CIT · 01-04-2008, 09:03 PM

ok, turns out I should have fully read the first post before I started on this - I completely missed the 8-lines rule until now

As such, the code below isn't my entry - I'll be off to make an 8-line entry now - but since I wrote it, might as well post it :D

I decided to use the Google Spreadsheet service to swap the values over (using the Zend Framework GData library)

This code requires you have a valid google account, a spreadsheet created with the same name as $spreadsheet in the code and the Zend Framework installed in /library.

PHP Code:


			
<?php



// The challange!

$a = 1;

$b = 2;



// Google Account details, spreadsheet name and worksheet name

$user = 'yourAccount@gmail.com';

$pass = 'secret';



$spreadsheet = 'talkphp_example';

$worksheet = 'Sheet1';



// Load the Zend bits

set_include_path('.' . PATH_SEPARATOR . './library' . PATH_SEPARATOR . get_include_path());



require_once 'Zend/Loader.php';

Zend_Loader::loadClass('Zend_Http_Client');

Zend_Loader::loadClass('Zend_Gdata');

Zend_Loader::loadClass('Zend_Gdata_ClientLogin');

Zend_Loader::loadClass('Zend_Gdata_Spreadsheets');



// Connect to Google

$authService = Zend_Gdata_Spreadsheets::AUTH_SERVICE_NAME;

$httpClient = Zend_Gdata_ClientLogin::getHttpClient($user, $pass, $authService);

$gdClient = new Zend_Gdata_Spreadsheets($httpClient);



// Fetch and set the spreadsheet

$feed = $gdClient->getSpreadsheetFeed();



foreach($feed->entries as $entry)

{

    if ($entry->title->text == $spreadsheet)

    {

        $key = split ('/', $entry->id->text);

        $spreadsheetId = $key[5];

    }

}



// Find and set the worksheet

$query = new Zend_Gdata_Spreadsheets_DocumentQuery();

$query->setSpreadsheetKey($spreadsheetId);

$feed = $gdClient->getWorksheetFeed($query);



foreach($feed->entries as $entry)

{

    if ($entry->title->text == $worksheet)

    {

        $key = split ('/', $entry->id->text);

        $worksheetId = $key[8];

    }

}



// Set A1 to $a and A2 to $b

$gdClient->updateCell(1,1, $a, $spreadsheetId, $worksheetId);

$gdClient->updateCell(1,2, $b, $spreadsheetId, $worksheetId);



// Fetch the cells

$query = new Zend_Gdata_Spreadsheets_CellQuery();

$query->setSpreadsheetKey($spreadsheetId);

$query->setWorksheetId($worksheetId);

$cellFeed = $gdClient->getCellFeed($query);



// Switch the values over!

foreach($cellFeed as $cellEntry)

{

    if ($cellEntry->cell->getRow() == '1' && $cellEntry->cell->getColumn() == '1')

    {

        // A1

        $b = $cellEntry->cell->getText();

    }



    if ($cellEntry->cell->getRow() == '1' && $cellEntry->cell->getColumn() == '2')

    {

        // A2

        $a = $cellEntry->cell->getText();

    }

}



// $a should now be '2' and $b should now be '1'

echo '$a: ' . $a . '<br />';

echo '$b: ' . $b . '<br />';

Dam 8 line rule! brb with a new entry :D

Alan

Wildhoney · 01-04-2008, 09:17 PM

Lol! Man, you're crazy

! That's why I made the 8 line rule. To stop people wasting so much time on something like this.

Alan @ CIT · 01-04-2008, 09:18 PM

Ok, my new attempt - using bitwise operators to swap the values about:

PHP Code:


			
<?php



$a = 1;

$b = 2;



$a ^= $b ^= $a ^= $b;



echo $a;

echo $b;

Alan

Alan @ CIT · 01-04-2008, 09:18 PM

Quote:

Originally Posted by Wildhoney

Lol! Man, you're crazy

! That's why I made the 8 line rule. To stop people wasting so much time on something like this.

It's ok, I got plenty of time to waste :D

Alan

Salathe · 01-04-2008, 09:29 PM

Disclaimer: I hold no responsibility for any physical or mental injury to yourself or those in your immediate vicinity caused as a direct result of looking at my method of swapping the variables' values. You have been warned.

PHP Code:


			
$a = 1;

$b = 2;



/* 1 */ $szStory = 'The quick brown fox jumps over the lazy dog. How awesome is that?';

/* 2 */ $aMess   = compact(array_unique(str_split(preg_replace('/[^a-z]+/', '', strtolower($szStory)))));

/* 3 */ foreach (array_reverse(array_keys($aMess)) as $iKey => $szVar)

/* 4 */     (isset($pMess) or $pMess = new stdClass) and $aTemp  = array_values($aMess) and $pMess->$szVar = $aTemp[$iKey];

/* 5 */ for($iPos = 0, $iLen = count($aPos = array(2, 17, -2, 8, 32, 2, -6)); $iPos < $iLen; $iPos++)

/* 6 */     (isset($szFunc) or $szFunc = '' or 0123 === 0x53) and $szFunc .= strtolower($szStory[$iPos + $aPos[$iPos]]);

/* 7 */ $szFunc(get_object_vars($pMess));

/* 8 */ unset($szStory, $aMess, $iKey, $szVar, $pMess, $aTemp, $iPos, $iLen, $aPos, $szFunc);



// Now, magically, $a = 2 and $b = 1... don't ask how.

header('Content-Type: text/plain; charset=utf-8');

var_dump($a, $b);

TlcAndres · 01-04-2008, 09:41 PM

I made this...then read the rules, I broke the majority of the rules

PHP Code:


			


<?

    $a = 1;

    $b = 2;    

    preg_match_all('/[1-9]/',serialize(array($a,$b)),$ar);

    $ar = reset($ar);

    foreach(array_keys($ar) as $k)

    {

        $r = next($ar);

        if(empty($ar[$k]) or $ar[$k] == $r)

        {

            unset($ar[$k]);

        }

        else

        {

            $a = $ar[$k];

            $a = ($a) + (40 / 2 - 10 * .5 - 5.5 * 2 << 5.5 >> 10);

            $ar[$k] = $a;

        }

    }

    $r = array_reverse(array_splice($ar,1));

    $let = 'a';

    while(list(,$v) = each($r))

    {

        $string .= chr(36) . $let . chr(61) . $v . chr(59);

        ++$let;

    }

    ob_start();

    eval($string);

    ob_get_clean();

    var_dump($a);

    var_dump($b);

?>

It was still fun though

(I know, nearly everything there is useless)

Alan @ CIT · 01-04-2008, 09:41 PM

Wow, that's insane Salathe :D Followed the code about halfway through then I'm fairly certain I blacked out :D

Another way to do it (if in doubt, use a database!):

PHP Code:


			
<?php



$a = 1;

$b = 2;



$db = sqlite_open('talkphp.db');

sqlite_query($db, 'CREATE TABLE talkphp (var varchar(2), val int)');

sqlite_query($db, "INSERT INTO talkphp (var, val) VALUES ('a', ". $a . ")");

sqlite_query($db, "INSERT INTO talkphp (var, val) VALUES ('b', ". $b . ")");

$vars_r = sqlite_query($db, 'select * from talkphp');

$vars_a = sqlite_fetch_all($vars_r);

$a = $vars_a[1]['val'];

$b = $vars_a[0]['val'];



echo $a;

echo $b;

Alan.

TlcAndres · 01-04-2008, 09:47 PM

I'm fairly certain this thread will be counter-productive to all those who have started to learn PHP

fun non the less though