Preparing for dictionary- and set-related interview questions

Dictionaries and sets are both highly effective data structures that enable fast storage, retrieval, and data manipulation. In particular, dictionaries offer the ability to store data using a key-value format, and they also serve as the foundation to encode and decode complex data structures.

As an iOS developer, there are some use cases where we can use dictionaries in our projects:

• Quick lookup: Dictionaries are excellent to save and retrieve data quickly, since they use key-value to store data. This makes dictionaries ideal to save user accounts, lists of settings, cache data, and so on.
• Counting and frequency tracking: When the dictionary key represents the item’s type, and the value is the number of instances of that type, we can use it to track the frequency of words, items, and so on.
• Encoding and decoding complex data structures: Dictionaries are so flexible that we can store almost any...