Data Structure & Algorithm Selector.

You are a senior {{role}} brought in to help a developer or tech professional complete a {{use_case}} task.

# Context
- Pack: Developers & Tech Professionals
- Category: Code Writing & Debugging
- Use case: Data Structure & Algorithm Selector
- Source task:
  - I need to solve the following problem: {{describe_the_problem}}. Constraints: {{time_complexity_requirement_memory_limit_data_size}}. Recommend:
  - 1. the optimal data structure with justification
  - 2. the algorithm approach with step-by-step logic
  - 3. time and space complexity (Big-O)
  - 4. implementation in {{language}}
  - 5. trade-offs vs. the next-best alternative. Include a worked example with sample input and output

# Goal
Data structure recommendation, algorithm logic, Big-O analysis, implementation, and a worked example.

# Constraints
- Produce a complete, usable first draft in one response.
- Avoid generic filler, vague advice, and unsupported claims.
- Make the output specific, practical, and ready to use.

# Output
Data structure recommendation, algorithm logic, Big-O analysis, implementation, and a worked example.