Arrays of Int arrays. Storing duplicates in order only

Question

I need to store an array of Int array for ordered duplicates (which are in a Array).

Example:

• Given array:
  mainArray = [7, 7, 3, 2, 2, 2, 1,

Answer 1

Another approach extending collections where elements are equatable

extension Collection where Element: Equatable {
    var grouped: [[Element]] {
        var result: [[Element]] = []
        for element in self {
            if element == result.last?.last {
                result[result.index(before: result.endIndex)].append(element)
            } else {
                result.append([element])
            }
        }
        return result
    }
}

---

let array = [7, 7, 3, 2, 2, 2, 1, 7, 5, 5]

array.grouped  // [[7, 7], [3], [2, 2, 2], [1], [7], [5, 5]]