Past challenges

Second of the returning challenges on mircscripts.org and it was another success. Thanks to all those who participated and I welcome those new to participating in challenges... hope you find it a rewarding experience. :)

The Challenge: Explained

The challenge was one of an unusual one that I came up with. You were given code to de-obfuscate. As quite a few have pointed out across the forum and in private messages - The code did give strange results if it was spread across multiple lines. You needed to analyse why it did this and what it was doing instead. In actual fact what was happening was a mIRC parser error between the two while loops that was on the same line. The while loop effectively turns into an if statement and only iterated once and it never actually 'looped' – To understand this, I’ve created an alias that will simulate the parser error:

alias parser-error var %a 1,%i 500 | while %i { while %a { echo -a %i | dec %a } | %a = 1 | dec %i }

Looking at this code you would expect it to echo from 500 to 1 on the screen. Instead, it only displays 500. If you were to spread this across multiple lines – It would execute as expected.

Hint

Some of you might have found the hint:

V2hpbGUgdGhlcmUgaXMgYSBtaXJjIHBhcnNlciBlcnJvciB5b3VyIGNvZGUgd2lsbCByZW1haW4gdmFsaWQu

Not much of a hint? In the rules was another 'secret' hint in which said '$decode is allowed.' Once you $decode(hint,m) you received the message:

While there is a mirc parser error your code will remain valid.

I'm not sure how many people found this out - It would be interesting to know in the forums after the results are posted. :)

Results

Out of the 20 entries - 9 were invalid and 11 were valid entries. Congratulations to the winner jaytea with 142 bytes and in second place E_TarDeD with 145 bytes. Due to the huge volume of tests upon the new $obs alias - Only the first failed test pattern will be shown.

I once again invite all those to participate in the next challenge. As always, suggestions for challenges are welcomed in private message to me.
Winner:

Invalid Entries

zzattack	145 bytes	$obs(tel4) returns $null instead of 81
Lam4o	155 bytes	$obs(Ty5QH0) returns 8D instead of 9E
xinion	159 bytes	$obs(TDID0ZFzPm) returns 4 instead of 118
LimonE	172 bytes	$obs(W) returns 3 instead of $null
foobar	223 bytes	$obs(6NtaWPyVcnx) returns 169 instead of 3
Mpdz	232 bytes	$obs(F) returns 3 instead of 2
[Znork]	244 bytes	$obs(1ypIQqG3S) returns $null instead of 104
hixxy	267 bytes	$obs(X9) returns 32 instead of $null
blink	325 bytes	$obs(D) returns 232032 instead of 2

Description:

new challenges as of 2006!

In this challenge you are asked to take the obfuscated code below and shorten it as much as possible.

The code has been deliberately made longer than necessary. You will need to understand what the code does in order to shorten it substantially. The code MUST return the same output as the code below.

Here is the code:


alias obs {
var %=, %$ 1,%%,%:,%:.,%l $len($1-) | while %$ <= %l { %= = $calc($asc($mid($1-,%$,1))/2.9+%=) | %$ = %$ + 1 } | %= = $left(%=,$pos(%=,.)) | %l = $iif(*0 iswm %l,9,$right(%l,1)) | %$ = 1 | while %$ <= $len(%=) { %: = $mid(%=,%$,%l)
while %: { %:. = $iif($calc(%: % ($asc(%)-21)) > 9,$chr($calc(5*11+$v1)),$v1) $+ %:. | %: = $int($calc(%: /($asc(/:.)-31))) } | %% = %% $+ $iif(%:.,$v1,0) | %$ = %$ + %l } | return %% }

Example:

$obs(z) = 4
$obs(123456) = 6A
$obs(?:@~0-+) = 9A
$obs('';,,.,//??///##=-2990425//:!::::!@#s]/) = 2AD

Hint: V2hpbGUgdGhlcmUgaXMgYSBtaXJjIHBhcnNlciBlcnJvciB5b3VyIGNvZGUgd2lsbCByZW1haW4gdmFsaWQu

Rules: