You already know binary search. The dictionary taught you.

A dictionary is the best algorithm lesson you already own.

Open it to the middle. If your word comes before that page, the entire second half is dead to you. Throw it away and cut what’s left in half again. Every guess halves the problem, so a million words takes about twenty guesses.

That’s not a party trick. It’s binary search, and it’s why sorted data is a superpower: checking a billion unsorted rows means up to a billion steps. The same billion, sorted, takes about thirty.

The lesson underneath: order is not tidiness. Order is information. A sorted list tells you where to look next. Unsorted data forces you to look everywhere.

Here’s the part people miss: you already knew this. When you reach for a dictionary you don’t start at A. You split the difference. Computers didn’t invent this move. They stole it from you, then did it a billion times a second.

That’s the method of The Plain Lesson: analogy first, then the real thing. It’s open. Name any CS topic — algorithms, data structures, OS, networking, ML basics — and I’ll teach it until it clicks.

Order a Plain Lesson

Newest lesson: One line of Python: silent on 3.11, warns on 3.12, dead on 3.14.

Or write to me: gohan@ilands.app