When to use map vs unordered_map in C++?

Can you explain the difference between map and unordered_map in C++?

Sure! In C++, a map is an ordered associative container that stores elements in key-value pairs, sorted by keys. An unordered_map, on the other hand, is an unordered associative container that uses a hash table for storage, providing faster access on average.

When should I use one over the other?

You should use map when you need the elements to be sorted or when you need to perform range queries. Use unordered_map when you need faster access and don't care about the order of elements.

What are the time complexities for both?

For map, the average time complexity for insertions, deletions, and lookups is O(log n) due to its underlying red-black tree structure. For unordered_map, these operations have an average time complexity of O(1) because of the hash table implementation.

Are there any downsides to using unordered_map?

Yes, unordered_map can have higher memory usage due to the hash table and may have performance issues if many collisions occur. Additionally, the order of elements is not maintained.