Same O(1), different performance: finding orders in an order book
The problem Many systems need to map one object to another, of the same or of a different type. This happens, for example, when they receive information in one form and want to convert it to another, or when they simply want to access information through a lightweight handle, called the key. The family of data structures that does this is called associative containers, and they are fundamental in most modern systems. There are many ways to implement one, depending on what the system needs, but by far the most common is the hash table. ...