[PheonixPharts]

> Asking me to solve an extremely esoteric problem that has zero relevance to my day-to-day

I'm always surprised how useless something is when I don't know it, and suddenly once I do know it, I solve lots of problems with it!

I've heard programmers grumble about how useless calculus is, before I learned calc I used to grumble about that too. After I learned it there were countless problems I unlocked solutions for by applying the thinking I learned in calculus.

I've heard programmers say that you'll never need to implement your own sort for mundane tasks, but, it turns out that after really grokking topological sort I used it countless times for fairly mundane problems like creating plots.

I've heard programmers say that learning the lambda calculus is a waste of time, and nobody uses functional programming. Yet it was people that understood these things that transformed Javascript from a useless browser oddity into one of the most widely used languages. It was seeing that Javascript was essentially a Scheme that unlocked it's true potential.

Over my career it's remarkable how many "esoteric problems" have lead to me solving hard tasks or even shipping entirely new products. If you're only focused on what is required of your day job today you're only going to be at best a mediocre engineer.

[ram_rar]

> after really grokking topological sort I used it countless times for fairly mundane problems like creating plots.

I'm interested in learning more - in what scenario was topological sorting essential for generating plots, and what specific problem did it solve?

[PheonixPharts]

Essentially a funnel report where you want to know the total percent of the population that has reached a given path, but you only know the output probabilities of each step in the funnel (node). This is a fairly common situation.

As a simple example: you know after signup 20% of customers purchase, 80% don't, but what you want to trivially add in is the fact that of the users in a marketing campaign, 10% of them signed up, which means for the marketing funnel 2% purchase. Now consider that you have 20 or more such events in your funnel and you want to combine them all with out doing all the math by hand. Likewise you want to be able to add a newly discovered step in the funnel at will.

Using a topological sort you can take an arbitrary collection of nodes where each node only knows that probability the next nodes are, sort them and then compute the conditional probabilities for any user reaching a specific node fairly trivially, given the assumption that your funnel does represent a DAG.

If you don't perform the topological sort then you can't know you have calculated all the conditional probabilities for the upstream nodes, which makes the computation much more complicated. Topological sort is very useful any time you have an implied DAG and you don't want to have to worry about manually connecting the nodes in that DAG.

[scottLobster]

That section was less complaining about the nature of the problem and more about the harshness of judging the solution. The irrelevance to day-to-day work merely emphasizes the unfairness of the judgement.

If I'm put on the spot, under time pressure, to solve a problem I've never seen before and will likely never see again on the job, AND you reject me because my solution was slightly incorrect or naive, well it's obvious what the nature of the job is at that point. You're filtering for candidates that can and will devote dozens of hours to Cracking the Coding Interview and LeetCode. Sorry, I have a full-time engineering job and two young kids, and you clearly don't value my capabilities or experience or time, you value my willingness to spend my extremely limited free time studying to ace your half-baked engineering IQ test, for the honor of possibly working for you.

I once had a company cancel a scheduled interview when I informed them I had received an offer from another company, but was more interested in them and was wondering if I could step up the interview schedule. They told me unless I was willing to reject the existing offer and submit to their multi-week interview process we couldn't move forward. Esoteric, irrelevant algorithm questions with strict judgements are just a different version of that same arrogance.