What are the best practices for using unordered_map in C++?

What are the best practices for using unordered_map in C++?

When using unordered_map in C++, consider the following best practices: 1. Use appropriate hash functions for your keys. 2. Reserve space if you know the number of elements in advance to avoid reallocations. 3. Use emplace() instead of insert() for better performance when constructing elements in place.

Can you explain why reserving space is important?

Reserving space in unordered_map is important because it minimizes the number of reallocations needed as elements are added. This can significantly improve performance, especially when dealing with large datasets.

What are some common pitfalls to avoid?

Common pitfalls include using non-hashable types as keys, not handling collisions properly, and assuming that the order of elements will remain consistent, as unordered_map does not maintain order.

How does unordered_map compare to map?

unordered_map offers average constant time complexity for lookups, insertions, and deletions, while map provides logarithmic time complexity. However, map maintains order, which unordered_map does not.