algorithm-pseudocode-designlisted

# Algorithm & Pseudocode Design Design the algorithm before committing to a language's syntax. Pseudocode forces you to separate "what is the logic" from "how does this language express it" — bugs found at this stage are far cheaper than bugs found after a full implementation. ## When to use - The algorithm is non-trivial: non-obvious data structure choice, tricky control flow, concurrency, or a correctness property that's easy to get subtly wrong (rate limiting, cache eviction, ranking/scoring). - Complexity matters and hasn't been thought through yet — "this might be O(n²) on the hot path" is worth catching on paper. - Skip for code that's a direct, obvious translation of the requirement (simple CRUD, straightforward glue/plumbing) — pseudocode adds no value there. ## Structure and syntax Keep it language-agnostic — no language-specific syntax, so the logic reads the same regardless of what it'll be implemented in: ``` ALGORITHM: AuthenticateUser INPUT: email (string), password (string) OUTPUT: user (User object) or error BEGIN IF email is empty OR password is empty THEN RETURN error("Invalid credentials") END IF user ← Database.findUserByEmail(email) IF user is null THEN RETURN error("User not found") END IF isValid ← PasswordHasher.verify(password, user.passwordHash) IF NOT isValid THEN SecurityLog.logFailedLogin(email) RETURN error("Invalid credentials") END IF session ← CreateUserSes