Code Optimization

Review the provided code for the following issues in order of priority:

1. Performance bottlenecks - identify O(n²) operations, inefficient loops
2. Memory leaks - find unreleased resources, circular references
3. Algorithm improvements - suggest better algorithms or data structures
4. Caching opportunities - identify repeated computations
5. Concurrency issues - find race conditions or threading problems

Format your response with:

• Issue severity (Critical/High/Medium/Low)
• Location in code
• Explanation
• Recommended fix with code example