JonC

https://mitpress.mit.edu/9780262046305/introduction-to-algorithms/

This one is pretty hardcore. I bought the 2nd edition of it over 20 years ago when I started my career as a developer due to not doing a CS degree.

Also take a look at the Specification Pattern for something similar.

That’s something I would only use if the logic becomes very complex, but it can help break things down nicely in those cases.

Why the assumption that reactivity is only a front-end thing?

I’ve used it plenty on the back-end when dealing with streams of data that need to trigger other processing steps.

And he created Trello

Same, using Chat GPT 4. It explained the steps without prompting, which is different from the single line answer shown in the post too. I got this…

Let’s break this down step by step:

1. Sally has 3 brothers.
2. Each of those brothers has 2 sisters.

Sally is one of those sisters for each of her 3 brothers. Therefore, the second sister that each brother has would be the same other sister.

This means that Sally has only 1 other sister, making a total of 2 sisters in the family (including Sally herself).

So, Sally has 1 sister.

That one’s actually really easy to prove numerically.

Not going to type out a full proof here, but here’s an example.

Let’s look at a two digit number for simplicity. You can write any two digit number as 10*a+b, where a and b are the first and second digits respectively.

E.g. 72 is 10 * 7 + 2. And 10 is just 9+1, so in this case it becomes 72=(9 * 7)+7+2

We know 9 * 7 is divisible by 3 as it’s just 3 * 3 * 7. Then if the number we add on (7 and 2) also sum to a multiple of 3, then we know the entire number is a multiple of 3.

You can then extend that to larger numbers as 100 is 99+1 and 99 is divisible by 3, and so on.