Easy-Level DSA

Start by clarifying the exact contract for Easy-Level DSA: input representation, mutation rules, duplicate behavior, and what should happen on invalid or empty input. The core idea is constraint-led selection of fundamental structures. Work a tiny example aloud and name the invariant after each step, because that is the proof that the approach stays correct as the input grows.

A dependable implementation plan is to clarify inputs and mutation rules; state a baseline; improve only when limits require; analyze hidden sorting or copying costs; test boundaries. Do not hide O(n log n) work behind an O(n) claim. Keep the code aligned with that invariant instead of adding special cases that silently change the contract. Test the smallest input, a normal case, duplicates or ties where relevant, an adversarial boundary, and a case that exercises the failure path. The expected complexity is depends on the actual task. Explain both time and auxiliary memory, including recursion or helper structures; do not hide sorting, copying, or repeated scans. If the title omits critical constraints, say what you need to know before committing to a more specialized solution.