Thesys QnA IV

Q: what’s the average O() complexity of insertion sort
AA: N^2 in most implementations — comparison-based, but using contiguous memory. NlogN if using skip list

Q: what’s the average O() complexity of heap sort
AA: NlogN, since it’s comparison-based.

Q: what are the synchronization primitives on the operating systems you know

Q: how many levels of caches are in a typical Intel processor
%%A: at least 3 possibly 4.
AA: some intel processors do have 4 levels

Q: name some IPC mechanisms
%%A: 1) shared mem 2) sockets 3) pipes

–2nd round (Don Bush?)

Q: Requirement: insert into a std::map only if key is absent
AA: the insert() function does that by default! Returns a pair<Iterator-where-inserted, bool-isInserted>. I used this same technique in my handleInputInternal()

Q: if my class Student has a private dtor, will it compile?
%%A: yes it’s possible to define a member function to invoke the dtor on a pointer passed in
%%A: deleting a ptr-to-Student won’t compile. Correct!
AA: have a friend call the dtor!

Q: Any guess why STL stack designer didn’t combine top() and void pop() like in other languages? hint: what if the copy ctor throws?
%%A: it’s more efficient if a function doesn’t need to return anything, so we don’t want to force the pop() users to pay a price for something they don’t need.

Q: do you create your own templates?
A: I should name the SFINAE hack!

Q: any restriction on a non-type template parameter’s type?
%%A: int and bool are common. Pointers are allowed. https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.2.0/com.ibm.zos.v2r2.cbclx01/non-type_template_parameters.htm shows even arrays and ptr-to-functions are allowed.
AA: has to be a discrete type, not a float

%%Q: what’s the usage of this non-type parameter?
A: std::array uses it for the size. It can’t be a ctor argument since if you construct an array on stack the size must be known at compile time.

Q: can you use new-arrays with shared_ptr? I think he wanted vector<shared_ptr>
%%A: if I have a new-array to store somewhere, then I think shared_array or scoped_array
A: how about shared_ptr<vector>?

Q: what if ctor failes in Foo * p = new Foo() // will memory leak?
%%A: i know it’s common practice to throw from ctor…

Q: name some c++11 features you used in your recent projects
%%A: unique_ptr, shared_ptr, auto, unordered_map, initializer list for vector/map

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