Can you explain what a Set data structure is?

The data structure Set is a collection of unique elements, where each element can only appear once. Main characteristics:

• Uniqueness — duplicates are not allowed.
• Unordered — elements do not have a fixed order.
• Fast lookup — operations like adding, removing, and checking for an element are usually performed in constant time.

In iOS (Swift), Set is implemented as a generic type, for example:

var fruits: Set<String> = ["Apple", "Banana", "Orange"]
fruits.insert("Mango")
print(fruits.contains("Apple")) // true

Set is useful when you need to store a collection without repetitions and quickly check for the presence of elements.