Find the shortest substring that contains every required character with enough frequency.
Use the sliding window pattern to design an efficient solution and explain the tradeoffs in your approach.
Examples
Input: See starter test cases Output: Expected result depends on the selected implementation Explanation: These local prompts are original practice stubs and can be replaced by backend-provided examples later.
Constraints
- Inputs follow the shape implied by the prompt title.
- Prefer an approach that matches the named pattern track.
- Optimize for clarity first, then improve time and space complexity.