Spaced Repetition

The one that I did this morning was:

If given the root of a binary tree, calculate the number of unival subtrees contained in the tree.

The back is usually either blank, or has a space and time complexity that I should get if I did it correctly.

It’s important to make sure you solve it at least once, and understand the solution well before you make a card of it.

There recently was another discussion related to spaced repetition[0], and at the time I dismissed it. I mostly thought "huh, bad memory never really held me back in software engineering, so I don't really care", and that with the fact that my factual memory is probably the worst it has ever been.

Fast forward a month. My biochemistry university studies have started, and I'm absolutely in love with spaced repetition. It's been one of the best learning experiences of my life. I don't think I've ever acquired that much (factual) knowledge about a new field in such a short timeframe, though there a probably other factors at play too, like motivation.

I write Anki cards on my computer and sync them to my smartphones, and then do them on my commute and before I go to sleep. Every time I go through some of my course material and encounter something where I'm not sure what it means, I note the word (with context) down in my notebook and then later sit down to write a Anki card for it.

The first exams for the semester are still to come, but largely thanks to spaced repetition, I feel very confident about them. Really looking forward to applying it in other parts of my life in the future!

[0]: https://news.ycombinator.com/item?id=19529236

I started off with just putting in a new vocabulary word every day and have been gradually ramping up the amount of info that I put into it. Now, I will add anything from programming details (e.g. how do you get the number of characters in a Rust string?) to key facts from the books I read (e.g. in The English Patient, who does the patient have an affair with?). My review sessions only take 5-10 minutes a day, and my only regret is not starting this habit earlier (especially in school). It's incredibly gratifying to review something, know the answer, and be very aware that without Anki, I would have forgotten it a long time ago.

[1]: http://augmentingcognition.com/ltm.html

1. Slow down your review session. I run into this problem mostly when I lose discipline and start skimming the question.

2. Put more effort into breaking info down into very atomic parts. For complex info, I'll still put in a high-level card, but I'll also put in cards that represent pieces of the info.

3. Add different cards for different methods of recall. I frequently add pairs of cards. For example, I added both "what is Betteridge's law?" and "what adage states that any headline that ends in a question mark can be answered with no?"

I had the same problem when I was initially only put in definitions into Anki. I was able to say the definition 1:1 but didn't form the concepts very well. My 2 (very similar) solutions for this (which I found to work pretty well), are:

1. Cross-referencing cards. I started editing a lot of cards, to add cross-references to other definitions that I also have cards for. For all the new cards I write now, I always try to have at least one reference to something that is on another card.

2. Meta-cards. I specifically add cards that test the knowledge of concepts, and me explaining it by adding cards like "Explain the difference between A and B".

3. Epic cards. When I started learning the periodic system of elements, along with the individual elements, I added a card for each group, a card for each group where I also have to know the element symbol, and a card for each group where I have to know the element symbol and atomic number. Obviously, I can only correctly solve a card if I know the easier versions of it, but it both provides a bigger goal to work towards, and also helps to put the smaller individual pieces of information I'm am learning into a context.