Coding Interview Horrorshows

The Something Awful Forums > Discussion > Serious Hardware/Software Crap > The Cavern of COBOL > Coding Interview Horrorshows

b0lt: Apr 29, 2005

FamDav posted:

There is no known linear time algorithm for Fibonacci that doesn't assume a machine that we cannot build.

There are no non-constant time terminating algorithms that don't assume a machine that we cannot build.

# ¿ Apr 16, 2016 23:06

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# ¿ May 10, 2024 02:48

b0lt: Apr 29, 2005

Centripetal Horse posted:

Wouldn't this do the job?
code:
int valueToTest = 212;
int bitsSet = 0;
while (valueToTest > 0) {
        bitsSet += valueToTest & 1;
        valueToTest >>= 1;
}
Maybe I am misunderstanding, because that seems way too easy to be tripping up anyone who has developed anything more complicated than Wordpress themes.

Now I really want a thread where one of you hiring managers posts all the tests you've had huge failure rates on so we goons can take stabs at the problems.

Aside from not working for negative values, yeah, this works.

If I were giving this as an interview question, it'd be as the first stage of a multistep problem, though. How would you make this faster?

# ¿ Jun 19, 2016 12:13

b0lt: Apr 29, 2005

hobbesmaster posted:

You can use it anywhere technically, https://isocpp.org/wiki/faq/freestore-mgmt#delete-this
I'm not sure its ever a good idea though?

It's illegal in a constructor for a type with non-trivial destructor, and in destructors always:

3.8.1 posted:

The lifetime of an object of type T begins when:
� storage with the proper alignment and size for type T is obtained, and
� if the object has non-trivial initialization, its initialization is complete

The lifetime of an object of type T ends when:
� if T is a class type with a non-trivial destructor (12.4), the destructor call starts, or

3.8.5 posted:

Before the lifetime of an object has started but after the storage which the object will occupy has been
allocated40 or, after the lifetime of an object has ended and before the storage which the object occupied is
reused or released, any pointer that refers to the storage location where the object will be or was located
may be used but only in limited ways.
[...]
The program has undefined behavior if:
� the object will be or was of a class type with a non-trivial destructor and the pointer is used as the
operand of a delete-expression

12.4.15 posted:

Once a destructor is invoked for an object, the object no longer exists; the behavior is undefined if the
destructor is invoked for an object whose lifetime has ended (3.8).

# ¿ Aug 23, 2016 18:37

b0lt: Apr 29, 2005

hobbesmaster posted:

Then thats #define class struct
And it should always work.

code:

#ifdef class
#error lol
#endif

# ¿ Aug 23, 2016 18:56

b0lt: Apr 29, 2005

hobbesmaster posted:

Unions are also classes if we're talking about C++ trivia.

I have no idea why.

More fun trivia: typedef is a storage class.

# ¿ Aug 23, 2016 21:01

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# ¿ May 10, 2024 02:48

b0lt: Apr 29, 2005

Hammerite posted:

I think if a valid answer to a question is "I don't know, why the hell would you do that in the first place" (as in the case of the "#define class struct" thing) then it is not a suitable interview question. I mean, if it's never going to come up with a sane team writing sane code then why do you care whether the candidate can work out on the spot what would happen? I think the examples of questions you gave in your post are solid, with the possible exception of the faulty machines one.

You should never do #define class struct, but you should be able to reason about what it would do, because you know the difference between a class and a struct.

# ¿ Aug 24, 2016 00:53

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