let array1 = ["user1", "user2", "user3", "user4"] let array2 = ["user3", "user5", "user7", "user9", "user4"] let intersection = Array(Set(array1).intersection(array2)) // ["user4", "user3"]
let array1 = ["user1", "user2", "user3", "user4"] let array2 = ["user3", "user5", "user7", "user9", "user4"] let intersection = Array(Set(array1).intersection(array2)) // ["user4", "user3"]