Comparison of Unordered Map and Ordered Map in C++11

What is the difference between unordered_map and ordered_map in C++11?

In C++11, an unordered_map is implemented as a hash table, providing average constant time complexity for lookups, while an ordered_map (std::map) is implemented as a balanced tree, offering logarithmic time complexity for lookups.

When should I use unordered_map instead of ordered_map?

You should use unordered_map when you need faster access times and don't require the elements to be in a specific order. It's ideal for scenarios where performance is critical.

Are there any drawbacks to using unordered_map?

Yes, unordered_map can have higher memory usage due to its hash table structure, and it doesn't maintain the order of elements, which might be necessary for certain applications.

Can you give an example of when to use each?

Sure! Use unordered_map for fast lookups in a large dataset where order doesn't matter, like counting word frequencies. Use ordered_map when you need to maintain sorted order, like implementing a priority queue.