Removing duplicate elements from an array in Swift

Question

I might have an array that looks like the following:

[1, 4, 2, 2, 6, 24, 15, 2, 60, 15, 6]

Or, reall

Answer 1

One more Swift 3.0 solution to remove duplicates from an array. This solution improves on many other solutions already proposed by:

• Preserving the order of the elements in the input array
• Linear complexity O(n): single pass filter O(n) + set insertion O(1)

Given the integer array:

let numberArray = [10, 1, 2, 3, 2, 1, 15, 4, 5, 6, 7, 3, 2, 12, 2, 5, 5, 6, 10, 7, 8, 3, 3, 45, 5, 15, 6, 7, 8, 7]

Functional code:

func orderedSet(array: Array) -> Array {
    var unique = Set()
    return array.filter { element in
        return unique.insert(element).inserted
    }
}

orderedSet(array: numberArray)  // [10, 1, 2, 3, 15, 4, 5, 6, 7, 12, 8, 45]

Array extension code:

extension Array where Element:Hashable {
    var orderedSet: Array {
        var unique = Set()
        return filter { element in
            return unique.insert(element).inserted
        }
    }
}

numberArray.orderedSet // [10, 1, 2, 3, 15, 4, 5, 6, 7, 12, 8, 45]

This code takes advantage of the result returned by the insert operation on Set, which executes on O(1), and returns a tuple indicating if the item was inserted or if it already existed in the set.

If the item was in the set, filter will exclude it from the final result.