Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

LINQ Ruined My Favorite Interview Question

scottchamberlin.tumblr.com

Post reply on HN
Print view View original

71–80 of 218 posts

Re: LINQ Ruined My Favorite Interview Question

#71

Post by corresation »

Strilanc wrote: post #70
corresation wrote: post #55

Earlier quoted context omitted.

but seriously, if you're writing c# and not using LINQ all the time You don't sound arrogant, but rather sound naive. I agree that someone who recruits surely should have known about and have experienced LINQ significantly by now, but the notion that you should be using it "all the time" is absolute nonsense. I avoid LINQ. I encourage others to avoid LINQ. It is almost always a sign of bad code. LINQ is syntactical s…

(Note: When I say LINQ I am referring to the functional style it encourages, not the query syntax. The query syntax is nice, but it's just a trivial syntactic transformation.) Correct me if I'm wrong, but the world is moving towards functional programming (i.e. LINQ) not away from it. Personally, I find LINQ far, far easier to read, write, and analyze. (On the other hand, I understand the deferred semantics and watch…

I'm not sure what you're actually arguing for or against. There is nothing at all wrong with functional programming, and such had nothing whatsoever to do with my comment. That LINQ happens to use some functional techniques doesn't make my criticism a criticism of fP.

Re: LINQ Ruined My Favorite Interview Question

#72

Post by jessedhillon »

spenuke wrote: post #68
shill wrote: post #31

Earlier quoted context omitted.

Without imports: d = {} for word in s1.split(' '): try: d[word] += 1 except KeyError: d[word] = 1 print [(x, d[x]) for x in sorted(d, key=d.get, reverse=True)][:10]

I'm a newbie, but the question seemed approachable so I went for it. This is what I came up with. (Python, btw.) def top_ten(s): words = s.split(' ') word_list = set(words) return sorted(word_list, key=lambda x: words.count(x))[:10] The question didn't ask for word counts, so I didn't see the need for a dictionary. I'd appreciate any advice on my solution. I'd be thrilled if I'm not too far off from being capable of…

This is a great approach. Even better because you carefully examined the requirements and found an interpretation which allowed you to make an optimization (words only, not counts, therefore sets are useful)

Re: LINQ Ruined My Favorite Interview Question

#73

Post by cema »

jameshart wrote: post #57
danabramov wrote: post #52

Earlier quoted context omitted.

Care to elaborate? It probably lacks punctuation characters, case-insensitiveness and RemoveEmptyItems option, but is there anything else missing?

中国四分之一地区六亿人受雾霾影响 contains more than one word.

Depends on the definition of a word. I18n is normally hard, and likely would make for an exciting discussion instead of just a tech interview.

Re: LINQ Ruined My Favorite Interview Question

#75

Post by Strilanc »

corresation wrote: post #71
Strilanc wrote: post #70

Earlier quoted context omitted.

(Note: When I say LINQ I am referring to the functional style it encourages, not the query syntax. The query syntax is nice, but it's just a trivial syntactic transformation.) Correct me if I'm wrong, but the world is moving towards functional programming (i.e. LINQ) not away from it. Personally, I find LINQ far, far easier to read, write, and analyze. (On the other hand, I understand the deferred semantics and watch…

I'm not sure what you're actually arguing for or against. There is nothing at all wrong with functional programming, and such had nothing whatsoever to do with my comment. That LINQ happens to use some functional techniques doesn't make my criticism a criticism of fP.

Functional languages use the concepts you're criticizing even more extensively than LINQ does.

Re: LINQ Ruined My Favorite Interview Question

#76

Post by cben »

untog wrote: post #42
jkrems wrote: post #25

Earlier quoted context omitted.

It looks like collections is part of the standard library: http://docs.python.org/2/library/collections.html . I think this disqualifies your JS solution, as long as doStuff isn't some fancy nodejs core module I missed.

I think the point still stands though, when you think of it as an interview question. The point is to get to the bottom of how the candidate would process such a query themselves, not to test their knowledge of the core libraries of their favourite language. I feel like that's what the post author meant when he said that LINQ had "ruined" the question- because it kind of does the same thing.

collections.Counter.most_common() uses heapq.nlargest() which is slightly more efficient than a full n*log n sort. But implementing a heap correctly from scratch is I guess outside the scope the OP intends for the interview question.

I would expect a good candidate to:

1. know that a heap is optimal here (remembering whether Counter uses it is optional)

2. express reluctance to implement it from scratch because surely the stdlib can do it better.

So IMHO using libraries like this ruins the question only in the sense of showing its not a challenge for the candidate. Something so simple should not take a page of code.

Re: LINQ Ruined My Favorite Interview Question

#78

Post by matchu »

spenuke wrote: post #68
shill wrote: post #31

Earlier quoted context omitted.

Without imports: d = {} for word in s1.split(' '): try: d[word] += 1 except KeyError: d[word] = 1 print [(x, d[x]) for x in sorted(d, key=d.get, reverse=True)][:10]

I'm a newbie, but the question seemed approachable so I went for it. This is what I came up with. (Python, btw.) def top_ten(s): words = s.split(' ') word_list = set(words) return sorted(word_list, key=lambda x: words.count(x))[:10] The question didn't ask for word counts, so I didn't see the need for a dictionary. I'd appreciate any advice on my solution. I'd be thrilled if I'm not too far off from being capable of…

The need for the dictionary shows up when your text gets significantly large. Each call to `words.count` is going to re-examine each word of the text to count 'em up, so, if n is the number of words in the text, and m is the number of distinct words in the text, then this solution is at least O(mn + nlog(n)) whereas the dictionary-based solution is O(nlog(n)). That is, we're re-reading the word list over and over, whereas the dict-based solution only reads it once. It's therefore more likely to be more efficient.

But I like the readability of this solution and there's a strong argument to be made for it on that basis, especially if the string is short. If this were a job interview, this would be a totally acceptable solution, though it'd be important to be able to discuss why other solutions might be faster and why you prefer this one anyway.

Re: LINQ Ruined My Favorite Interview Question

#79

Post by kyllo »

colanderman wrote: post #43
llambda wrote: post #8

I hate to be the bearer of bad news, but I think there may be even simpler solutions to this problem: (take 10 (reverse (sort-by (comp first rest) (frequencies (string/split ... #"\+s")))) The above is a Clojure one-liner example that I believe satisfies the original problem. So while LINQ may have simplified from the C-language family solutions he had seen, it's clearly possible to take it one step further with the…

expressivity of modern languages like Clojure Uh, no. Your solution just uses a bunch of standard library functions (at least, I hope they're not syntactic forms… and why a function as specific as "frequencies" not in some namespace boggles my mind). I could write that in C with an appropriate standard library. Ironically, expressing this in something like SQL actually speaks to the expressivity of the language becau…

So, the line of code in the OP that's missing from the LINQ version of the solution is:

    Imports System.Linq
Post reply on HN