71–80 of 243 posts
Earlier quoted context omitted.
You have a single question that is always present in your "initial code screen"? XOR-only questions are poor unless you're interviewing someone for a very specific kind of role.
> You have a single question that is your "initial code screen"? He never claimed that. It could just be part of the screen
Careful abusing these tricks. Over 10 years ago I decided to implement an RC4 (arcfour) cypher to generate pseudorandom noise for a test program. The algorithm looks like (from wikipedia): i := 0 j := 0 while GeneratingOutput: i := (i + 1) mod 256 j := (j + S[i]) mod 256 swap values of S[i] and S[j] K := S[(S[i] + S[j]) mod 256] output K endwhile Being a smartass 1337 coder (and declaring intermediate variables alway…
I sometimes use your "bug" on purpose in tests, when checking that two values are either both defined or both undefined, but not one defined and one undefined: $ python >>> a, b = 1, 2 >>> bool(a) ^ bool(b) False >>> a, b = 1, 1 >>> bool(a) ^ bool(b) False >>> a, b = None, None >>> bool(a) ^ bool(b) False >>> a, b = None, 1 >>> bool(a) ^ bool(b) True (Note: this doesn't work if a value can be 0, because bool(0) is Fa…
What works flawlessly, however, is:
In [1]: a = None
In [2]: b = 0
In [3]: (a is None) ^ (b is None)
Out[3]: True
In [4]: (a is None) != (b is None)
Out[4]: True
In [5]: a or b
Out[5]: 0
In [6]: b or a
Out[6]: None # should be 0
In [10]: a if a is not None else b
Out[10]: 0Careful abusing these tricks. Over 10 years ago I decided to implement an RC4 (arcfour) cypher to generate pseudorandom noise for a test program. The algorithm looks like (from wikipedia): i := 0 j := 0 while GeneratingOutput: i := (i + 1) mod 256 j := (j + S[i]) mod 256 swap values of S[i] and S[j] K := S[(S[i] + S[j]) mod 256] output K endwhile Being a smartass 1337 coder (and declaring intermediate variables alway…
{int i; for(i=0; i> There are a whole bunch of popular interview questions As a very personal strong opinion, this makes me groan. I'm not concerned If someone happens to know some esoteric trick that they could Google search (Unless of course you're applying for a position at a company that manufactures very low level devices like microcontrollers or embedded systems and questions like this are _actually relevant_). I'd rather know w…
I think it kind of depends on the type of programmer one wants to hire. There are different roles, solving different types of problems. There are places for people with technical brilliance, there are places for people with social brilliance, with both, and with neither. That's healthy. You want a diverse economy with different types of positions for different types of folks, and vice-versa. If I ask a half-dozen que…
There are lots of socially brilliant people out there, it's what many of us spend at least 20 years of our lives practicing.
Why would being a brilliant socializer command the same salary that a brilliant engineer does?
A fun party trick not mentioned here is reducing storage in a doubly linked-ish list: Normally each node stores 2 pointers: struct Node {void * prev;void * next} The trick is to use only 1 'pointer', storing prev XOR next: struct Node {void* xored;} While traversing, you remember not only the current position, but also where you came from. So forward traversal goes: next= current.xored XOR previous. Backwards also wo…
One of the coolest XOR tricks I've seen is fast encoding of negative integers to positive integers (unsigned) employed by ProtoBufs. It is called ZigZag encoding where negative and positive integers are interleaved such that lower negative values are assigned to lower positive values: input zz(int) 0 0 1 2 2 4 3 6 -1 1 -2 3 zz(n int64) => (n > 63) unzz(n int64) => (n >> 1) ^ (-(n & 0x1)) https://developers.google.com…
Edit: Looks good now!
> There are a whole bunch of popular interview questions As a very personal strong opinion, this makes me groan. I'm not concerned If someone happens to know some esoteric trick that they could Google search (Unless of course you're applying for a position at a company that manufactures very low level devices like microcontrollers or embedded systems and questions like this are _actually relevant_). I'd rather know w…
Perhaps such interviews are overused but if the interview is purely soft, and about "sell yourself to me", you will also be biased towards some people.
I mean of course it's important to be able to work together in a pleasant way, but when someone's main strengths are in the technical aspects, they may like to be able to showcase that too. And yes of course in the age of high level frameworks and glued CRUD pruducts, some programming jobs are more social than technical. But not necessarily all.
And I'm seeing lots of this sentiment nowadays on social media, that all "allegedly" merit based nerdy "gatekeeping" is merely about white male privilege and hence not inclusive.
A very good explanation of the algorithm: http://blog.notdot.net/2012/01/Damn-Cool-Algorithms-Fountain...
Earlier quoted context omitted.
Why does mov'ing a constant end up having overhead?
It's not overhead, it's about dependency breaking. 32-bit xors on a single register are universally recognized as a zeroing idiom, which means the CPU doesn't have to wait for the results of previous operations in order to set the value of the applicable register to zero. In modern CPUs zero'ing idioms aren't even executed, they only get as far as the register allocater. The register allocater will allocate a zero'd…