As a programming enthusiast i loved this one. Would you care to explain how you used kubernetes to develop this application ? More on reddit.com

Well, since it sounds like you're learning, I'll walk you through my though process in figuring it out. Unfortunately I probably have some background knowledge you lack, but that's nbd- I'll try to explain as I go along. First things first, I googled CoderPad and found this . Looks pretty similar to jsFiddle, codepad.org, etc. Cool! I pressed OK twice and ended up with a ruby environment - code editor on the left, with a run button, rbi console on the right. So the interesting thing here is that CoderPad is executing Ruby code for us (whether from the browser or console). So I want to figure out if it's executing the code remotely, on a CoderPad server, or compiling it to JavaScript or something and executing it locally. I right click on the page and select 'Inspect Element' and then navigate to the 'Network' tab (I suggest you use FireFox or Chrome for this). This tab gives us info on the communication between our browser and remote servers over the network. So now I'll run the default code in the editor. If there is activity in the 'Network' tab, it suggests CoderPad is running the code remotely. If there's no activity, then CoderPad is definitely running the code in the browser. I run the code and... no network activity! So, CoderPad is compiling the Ruby code in the editor and running in the browser somehow. And then I checked out the source under the 'Sources' tab and found this

The REPL uses Pry to provide a REPL with history, highlighting, and autocomplete. Additionally, whenever you run scripts... Strangely enough, there are descriptions of how all their runtime environments work in the source code of the page, even though they aren't visible. Weird. So anyway, if you got that far and have the developer tab open with the console, source code, networking and and more, I suggest you poke around in there and see what you find. Happy hacking!

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The problem occurs here

return(temp);

You are creating a temporary object that has allocated memory. When you return it, it's copied, and the value of the pointer is copied to the new Vector. But then the temporary goes out of scope and the destructor calls delete[] on that pointer. So now the new Vector has a pointer to invalid memory which it frees when it too goes out of scope. The same happens with the parameter to operator^ because its passed by value.

* Actually, the compiler can optimize away the copy due to the return. It's most likely due to the parameter being passed by value instead of by reference, though both are possibilities if the optimization is not done.

Because you're dynamically allocating memory, you should also define a copy constructor and assignment operator to correctly handle the memory transfer.

I suggest an alternate implementation where you use a std::map<int, double> instead of an array to store the coefficients where they are keyed by the term to which they apply. This will allow you to store sparse vectors much more efficiently without adding much complexity to your multiplication.

v = new double;

You don't need to do this since you set it to zero right after. It causes a memory leak.

** I added some extra print statements so you can see what's happening: http://codepad.org/TlvkvE99

The output indicates the temporary is being copied when it returns, then the one declared inside the function goes out of scope, then the copy is assigned to Z, and the copy goes out of scope, which is the second free of the same memory.

You won't always see the same output, however, as it will be compiler and system dependent. For example, on my system, it does the optimization and happily takes no action for the second free.

Constructing x
Constructing y
Constructing temp
-0.5
-0.5
-0.375
// no second "Constructing y" message because it uses the compiler-generated copy constructor for the parameter
Destructing temp : 0xa0380b8 // temporary
Destructing y : 0xa038058 // parameter
-0.5, -0.5, -0.375
Destructing temp : 0xa0380b8 // Z - it was assign the value of temp
Destructing y : 0xa038058
Destructing x : 0xa038020

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i interviewed with FB using coderpad and no the code wasn't compiled/run. actually i was given a method signature with hypothetical arguments and asked to implement starting with that. so it was impossible to start with main() and do the whole thing. More on reddit.com