What are the differences between a data structure Set and an array in terms of their usage and characteristics?

A Set and an Array are different data structures with distinct characteristics and uses:

• Uniqueness of elements: Set stores only unique values; duplicates are automatically ignored. An array can contain repeated elements.

• Order of elements: In an array, the order of elements is fixed and important; you can access elements by index. In a Set, order is not guaranteed (in Swift, Set is unordered), so indexing is not possible.

• Access by index: Arrays allow quick access to elements by index. Sets do not support indexed access.

• Search and membership check: Checking for the presence of an element in a Set is usually faster (close to O(1)), while in an array it is a linear search (O(n)).

• Usage: Arrays are convenient when order matters and duplicates are allowed. Sets are suitable when you need to store unique elements and quickly check their presence.

Example in Swift:

var array = [1, 2, 2, 3]
var set: Set = [1, 2, 2, 3]
print(array) // [1, 2, 2, 3]
print(set)   // [2, 3, 1] — order is not guaranteed, duplicates are removed