Check if elements in two arrays are same irrespective of index

Question

Suppose if I have two arrays - array1 and array2

let array1 = [\"abc\",\"pqr\",\"xyz\"]
let array2 = [\"pqr\", \"xyz\", \"abc\"]
         


        

Answer 1

Using counted sets as in Compare two arrays with the same value but with a different order works in Swift as well:

let set1 = NSCountedSet(array: array1)
let set2 = NSCountedSet(array: array2)
print(set1 == set2)

This works well for strings, numbers, and other values which are mapped to corresponding Foundation types NSString, NSNumber, etc. It might give unexpected results when used with custom structs.

For a pure Swift solution, count the number of occurrences of each element in the arrays:

func countMap(array: [T]) -> [T: Int] {
    var dict = [T: Int]()
    for elem in array {
        dict[elem] = (dict[elem] ?? 0) + 1
    }
    return dict
}

and compare the resulting dictionaries:

print(countMap(array: array1) == countMap(array: array2))

Alternatively – if the array elements are Comparable – compare the sorted arrays:

print(array1.sorted() == array2.sorted())