Easy DSA

Start by clarifying the exact contract for Easy DSA: input representation, mutation rules, duplicate behavior, and what should happen on invalid or empty input. The core idea is mapping a concrete operation to a simple, defensible pattern. 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 ask for operation and constraints; identify lookup order window or traversal signal; choose basic structure; state invariant; test edge cases. Easy questions still require duplicate and empty-input handling. 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 chosen operation. 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.

Complexity: For the usual one-pass version over n elements, use O(n) time and O(1) auxiliary space unless the requirement needs a map or set.