strings
2 free lessons tagged strings across Programming, Computer Science. Each one is a short sequence of focused steps with narration and a five-question quiz at the end — take them in any order, no signup required.
What a Program Is: Values, Variables, and Your First Script
Start from zero: what a program actually is, how to run Python in the shell or as a script, the four basic types, arithmetic expressions, variables as names, strings and f-strings, and why input() always hands you text. You finish by writing a working bill-splitting program.
Tries and Radix Trees: Structures Keyed by Prefix
A trie stores keys in their spelling rather than hashing them, which buys the one query a hash table cannot answer: find everything starting with this. This lesson covers the trie, the memory problem that makes it impractical, and the radix compression that fixes it and routes the internet.