Filter ads by a single rule

## Single-Rule Ad Filter ### Context When a user watches content, the system needs to filter an ad pool to find ads that match **one rule**. Implement a lightweight filter that supports a **single rule** with an **operator**. ### Data model **Ad** - `id: String` - `targetLocations: Set<String>` (e.g., `{ "CA", "TX" }`) - `age: int` (intended viewer age for the ad) **Rule** - `targetLocations: Set<String>` (optional) - `minAge: Integer` (optional) - `maxAge: Integer` (optional) - `operator: "AND" | "OR"` ### Matching semantics - **Location match**: if `rule.targetLocations` is present and non-empty, then an ad matches the location constraint if `rule.targetLocations ⊆ ad.targetLocations` (i.e., the ad targets *all* locations required by the rule). - **Age match**: - if `rule.minAge` is present, require `ad.age >= rule.minAge` - if `rule.maxAge` is present, require `ad.age <= rule.maxAge` - Combine the (present) constraints using `rule.operator`: - `AND`: ad must satisfy **all** present constraints - `OR`: ad must satisfy **at least one** present constraint - If a constraint is absent, ignore it. ### Input / Output - **Input**: `List<Ad> ads`, `Rule rule` - **Output**: `List<String>` of matching `ad.id` values, **preserving the original input order** ### Example Rule: `minAge = 21`, `targetLocations = {"US"}`, `operator = AND` Ads: - `A`: `age=21`, `targetLocations={"US","CA"}` → match - `B`: `age=13`, `targetLocations={"US"}` → no (age) - `C`: `age=25`, `targetLocations={"CA"}` → no (location) Output: `["A"]` ### Constraints (assume) - `ads.length` can be large; keep it efficient. - Location strings may vary in case; clarify/handle consistently (e.g., normalize to upper-case) if needed.