Day 13/60: HashSet patterns

60 Day Rust DSA Challenge

Today I focused on using Rust hash-based collections deliberately instead of treating them like magic storage. The strongest checkpoints were make the key and the stored meaning explicit before the map starts growing, update the hash state in the right order so the answer check stays correct, and use HashMap and HashSet for a defined reason instead of by reflex.

The mistake I wanted to avoid was building the right map but updating it in the wrong order. The day felt better once the invariant stayed visible and each update had one job.

The goal for tomorrow is simple: keep the rule clear enough that the next variation still feels related to the same idea. I also want to keep tracing tiny examples because they expose weak assumptions faster than large random tests. I also want to keep tracing tiny examples because they expose weak assumptions faster than large random tests.