How to quickly check if one collection is contained in another: using an array or a set?

Set (Множество) is faster for checking element inclusion.

Explanation:

• Array: Checking if an element is included in an array takes O(n) time on average, where n is the number of elements. To check if one collection is included in another, n iterations are needed, each of which is O(m), where m is the size of the second collection. Total: O(n*m).
• Set: Checking if an element is included in a set takes O(1) time on average. To check if one collection is included in another, n iterations are needed, each of which is O(1). Total: O(n).

Example with a set:

1. Create a Set from the first collection.
2. Iterate over the second collection, checking each element for inclusion in the created Set.

let collection1: [Int] = [1, 2, 3, 4, 5]
let collection2: [Int] = [2, 4]

// Create a set from collection1
let set1 = Set(collection1)

// Check if collection2 is a subset of collection1
let isSubset = collection2.allSatisfy { set1.contains($0) }

print(isSubset) // Will output true