What types of collections exist in Swift?

There are three main types of collections:

• Arrays: An ordered collection of elements of the same type. Access by index.
• Sets: An unordered collection of unique values of the same type. Efficient element existence check.
• Dictionaries: An unordered collection of key-value pairs. Keys must be unique and of the same type, values of the same type. Access by key.

Examples of creation:

// Array of strings
let fruits: [String] = ["Apple", "Banana", "Cherry"]

// Set of integers
let primeNumbers: Set<Int> = [2, 3, 5, 7, 11]

// Dictionary with String keys and Int values
let ages: [String: Int] = ["Alice": 30, "Bob": 25, "Charlie": 35]

Arrays and dictionaries are ordered in terms of traversal of elements in a loop, although their main characteristic is access by index or key, respectively. Sets do not guarantee traversal order.