Programming 3 luck

Put your programming skills to the test in these challenges.

Re: Programming 3 luck

Post by prince_caspian on Tue Jun 17, 2008 7:04 pm
([msg=5078]see Re: Programming 3 luck[/msg])

So modify the set_time_limit, if it's php it takes care of the response time.
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Re: Programming 3 luck

Post by sharpskater69 on Wed Jun 18, 2008 2:54 pm
([msg=5172]see Re: Programming 3 luck[/msg])

MrRubix wrote:Still working on it, but I think it'll be okay if I give it some more thought.

My main issue is speed. How fast have people gotten this down to?

I'm running it on a server and it times out after 30 seconds of processing, which is a bit annoying.


Depending on the input data, anywhere from < 2 seconds to a minute and a half.(C++)95% of them seemed to be under 2 minutes though. Compiled languages may be the answer if speed is a problem.

Be assured, you can't reverse this. It's basically a big binary tree with a lot of "dead branches" (impossible combinations). Since this can be solved with the right hash, that will be your goal, then everything else is plugged in to the algorithm(given). For that hash, looping is not what needs to be done though, think of an alternative.
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Re: Programming 3 luck

Post by MrRubix on Sat Jun 21, 2008 1:17 am
([msg=5404]see Re: Programming 3 luck[/msg])

Ahahaha I am feeling pretty happy right now. Finally got this mission completed! It only took about 15 seconds to find the correct solution, but only after many restarts (the other trials were less than satisfactory, but some test output gave me a good idea how to adjust certain parameters).

The real challenge of this mission is developing a smart brute-force system. I probably did it in a way that was different from what you were supposed to do, but it still works -- the idea is NOT to simply brute-force every single possible permutation. The reason for this is because you have a lot more information than you may think -- assumptions you can make and variables you can use to your advantage to make brute-forcing much more efficient.
Last edited by MrRubix on Sat Jun 21, 2008 11:26 am, edited 1 time in total.
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Re: Programming 3 luck

Post by raskL on Sat Jun 21, 2008 5:26 am
([msg=5411]see Re: Programming 3 luck[/msg])

well this is how i went about it, if this is breaching the rules or spoiling the task please remove :

-Removed- Yes it is spoiling the task, idiot! How many people are going to just go ahead and copy that code now? Warned and I'm also double warning you on HTS. Nice going.
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Re: Programming 3 luck

Post by raskL on Sat Jun 21, 2008 1:13 pm
([msg=5429]see Re: Programming 3 luck[/msg])

my apologies, i didnt read thro the posts and rules properly, i thought that posting up some code would be helpefull to people that are struggling. cos after all directly copying it would defeat the whole object of doing the task in the first place.
my bad.
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Re: Programming 3 luck

Post by sharpskater69 on Sun Jun 22, 2008 2:12 pm
([msg=5508]see Re: Programming 3 luck[/msg])

Just a reminder for anyone having problems, you need to get over the hurdle of understanding the code before you try to crack the algorithm it gives you. I'll be glad to explain any of the code to you (on the forum, in a post). Also, don't discard any variable or think it's not important. Part of coming of with a check is seeing what happens with certain variables.
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Re: Programming 3 luck

Post by MercyMe on Sun Jul 06, 2008 9:32 pm
([msg=6714]see Re: Programming 3 luck[/msg])

I think it's a good level actually =,=
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Re: Programming 3 luck

Post by aalpie on Thu Jul 17, 2008 8:31 am
([msg=7626]see Re: Programming 3 luck[/msg])

sharpskater69 wrote:Be assured, you can't reverse this. It's basically a big binary tree with a lot of "dead branches" (impossible combinations). Since this can be solved with the right hash, that will be your goal, then everything else is plugged in to the algorithm(given). For that hash, looping is not what needs to be done though, think of an alternative.


really good hint. I finally completed the level with good time(about 20-60 seconds). Just look for what you are trying to archieve and what you need to know in order to archieve this. Let your program brute-force the unknowns in an efficient way (think of the hint above given by sharpskater69).
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Re: Programming 3 luck

Post by gtrrkicw on Wed Aug 13, 2008 11:24 am
([msg=9572]see Re: Programming 3 luck[/msg])

I just finished this challenge after about a day of work. After a bit of optimizing my program will crack the challenge in a few seconds (less than 5) every time.

The best hint I can give is take a damn good look at how the sample output file is structured and use it to eliminate dead ends in your brute forcing.
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Re: Programming 3 luck

Post by kl223 on Thu Sep 25, 2008 3:09 pm
([msg=12525]see Re: Programming 3 luck[/msg])

gtrrkicw wrote:I just finished this challenge after about a day of work. After a bit of optimizing my program will crack the challenge in a few seconds (less than 5) every time.


Yep, my solution also took about a day of work and it decodes any input in less than a second. (written in C)
Anyway, thanks for this challenge. It was fun. :)

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