timv · HackerLangs

一昨日議論

And there lies the tradeoffs you need to consider as part of an interview question.

But if the best alternative is to sort the whole collection, then Quickselect doesn't introduce a new problem. You either accept that modifying the collection in place is an acceptable behaviour (and describe that in your API docs) or you make a copy of the collection and operate on that.

Given a choice between quickselect and quicksort, quickselect will get the answer with less overhead and no additional constraints (because it's essentially the same algorithm with unnecessary steps removed).

There are alternative approaches that don't require a full copy/sort, but they either require a partial copy + partial sort, or multiple passes through the collection.

timv

一昨日議論

You can use Quickselect (https://en.wikipedia.org/wiki/Quickselect) or Floyd-Rivest (https://en.wikipedia.org/wiki/Floyd%E2%80%93Rivest_algorithm)

Quickselect is fairly simple to understand if you already understand Quicksort. You use use a binary division but you avoid sorting sections where the order doesn't matter.

Let's start with a 7 element array

    [ 2, 4, 7, 5, 3, 6, 1 ]

We pivot on the mid-point (5) so that values less than end before it in the array and numbers larger end up after it

    [ 2, 4, 3, 1, 5, 7, 6 ]

Since 5 is now at an index greater than the midpoint, you know the median must be less than 5, so you don't care that 7 and 6 aren't sorted.

We pivot the first partition (first 4 elements) on 3 and get

   [ 2, 1, 3, 4, 5, 7, 6 ]

We don't care that 2 and 1 are unsorted, because we know that the median is > 3 (3 is at index #2 and we want index #3), so the median must be 4

timv

5 日前議論

> You mention early in the article that you intended to base this approach as a response to your own subpar user experience with support in other products.

This was the biggest (1) complaint for me - in light of what you discovered from your actual support experience, why was your expectation so off?

Was it that you expected support to be full of "how do I do this complicated thing?" questions that can be answered by an expert? That's an unrealistic expectation, but I guess now you know.

Or was it that you really thought that customers would be happy if you just took the time to explain your pricing model to them (also unrealistic).

It is kind of obvious from the types of emails you get, and the types of responses you give that it was not going to lead to strong customer relationships. If all you're doing is writing a 100 words to say "No, I'm not going to do what you want" that's not going to make things better.

(1) Actually 2nd biggest - the biggest was talking about "buying Castro" but having no explanation/links about who the author is, what Castro is, or how/when/why it was bought.

timv

2 か月前議論

I wrote something like that about 15 years ago for a financial institution.

For what we needed, we intentionally wanted both people to be at the same terminal (it was going to be used to give shell access to a specific unix account that ran a critical system).

That mean that we could implement it as a setuid (root) binary that required both users to authenticate. It had a config file that worked like sudoers, and defined a list of commands that could be called, how many people were needed to authenticate, and which unix groups they had to belong to.

timv

3 か月前議論

Imagine you were making purchasing decisions about which LLM-based coding tool to use.

If one of the possible vendors convinces you that that they have a next gen model that is so powerful it found 20+ year old bugs in a hardened operating system, that would undoubtedly have an influence on your decision even if you are only buying the current model.

timv

9 か月前議論

The argument here is that they're confident that the bounds check isn't needed, and would prefer the compiler not insert one.

The choices therefore are:

1. No bound check

2. Bounds check inserted, but that branch isn't covered by tests

3. Bounds check inserted, and that branch is covered by tests

I'm skeptical of the claim that if (3) is infeasible then the next best option is (1)

Because if it is indeed an impossible scenario, then the lack of coverage shouldn't matter. If it's not an impossible scenario then you have an untested case with option (1) - you've overrun the bounds of an array, which may not be a branch in the code but is definitely a different behaviour than the one you tested.

コメント