Ke Colin Zheng

This is not about a cheap Chinese student looking for get-arounds to pirating. It’s just once a while, we encounter secured pdf files that we get denied to copy/paste/print its content even for good deeds.

I have tried a bunch of approaches, including:

• Print the pdf using free 3rd party pdf writer such as Cutepdf to get the unlocked version: This doesn’t work for me.
• Use Advanced PDF Password Recovery Application:  This works, but you have to pay in order to get the full version of apdfpr.
• Use the Free PDF Unlock Online Utility: This works like breeze.I upload the pdf, and get back the unlocked version! Note you have to use IE7 so that the unlocked version can be saved.

So, here comes to my recommendation:
if you need a quick dirty hack, and the file is not classified or super sensitive, you can get it done easily using ensode’s free online service. And it works!

*Repeat: I’m not teaching you how to pirate proprietary documents. And I don’t get paid by ensode to promote their service. I have faith that you will use this trick properly for the good!

I am always a big fan of puzzles. And the fact that I’m graduating and hunting for jobs gives me the best reason/motivation for cracking them. 

I was checking the Facebook Puzzles today. Facebook engineers have done a great job motivating their puzzles. Well, for someone with a computer science background, some of their puzzles are clearly classical CS problems. 

“It’s A Small World” problem has another name in CS: the k-nearest neighbor problem. Instead of checking with every datapoint, the solution to the problem could be accelerated by limiting the search to certain regions only, which can be achieved with KD-tree. ANN(approximate nearest neighbor) is a good example of such approaches. 

“User Bin Crash” problem is a classical dynamic programing problem. Once you follow the DP approach to nail down the metric, the break-down and the initial value, it’s a shoe-in DP problem. 🙂

Now that I have done the “snacks”, I’ll start thinking about the harder ones…

btw: I’m not providing any solutions to the puzzles, just my 2 cents on how to crack them. 🙂