Building an O(1) LRU cache in C++ and Why It’s Harder Than It Looks

📰 Medium · Programming

Learn to build an O(1) LRU cache in C++ using std::list and std::unordered_map, and understand the concurrency challenges involved

advanced Published 23 May 2026
Action Steps
  1. Implement an LRU cache using std::list to store the order of elements
  2. Use std::unordered_map to store the keys and their corresponding values for O(1) lookup
  3. Handle eviction by moving the least recently used element to the front of the list
  4. Consider concurrency and thread safety when implementing the cache
  5. Test the cache under concurrent access to ensure correctness and performance
Who Needs to Know This

This lesson is beneficial for software engineers and developers who work with caching systems and need to optimize their performance, especially in concurrent environments

Key Insight

💡 Using std::list and std::unordered_map can achieve O(1) eviction in an LRU cache, but concurrency requires careful consideration

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🚀 Build an O(1) LRU cache in C++ with std::list and std::unordered_map! 💡 But beware of concurrency gotchas 🤯
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