What are the differences between std::map and std::unordered_map in C++17?

What are the differences between std::map and std::unordered_map in C++17?

In C++17, std::map is an ordered associative container that stores elements in a specific order based on keys, while std::unordered_map is an unordered associative container that uses a hash table for storage, providing faster average access times.

Can you explain the performance differences between the two?

Sure! std::map has O(log n) complexity for insertions, deletions, and lookups due to its underlying balanced tree structure. In contrast, std::unordered_map offers average O(1) complexity for these operations, but in the worst case, it can degrade to O(n) if many elements hash to the same bucket.

When should I use one over the other?

Use std::map when you need ordered elements or require range queries. Opt for std::unordered_map when you prioritize performance and don't need order.

Are there any specific use cases for std::unordered_map?

Yes! std::unordered_map is great for scenarios like caching, counting occurrences of items, or implementing lookup tables where fast access is crucial.