How to split a sequential integer array, if any sequence is missing - arrays

Question

Supposre I have an input array of integers. I want to split this array in multiple array based on the missing integer and append it in a new Array. I think split can be used here but not sure how to do it. I want arrayFinal only.
myArray = [0,1,2,4,7,8]
Desired Output
arrayOne = [0,1,2]
arrayTwo = [4]
arrayThree = [7,8]
arrayFinal = [[0,1,2], [4], [7,8]]

Answer 1

That's an algorithm you're asking for so there are a dozen different ways to do it. Since you are going to have to walk through the array's contents to find the missing integers, I would just create an array and append the numbers to it as you go, then create a new array whenever you hit a gap.
You'll probably have to adjust this for any special cases you might have. "Will this always start at 0 and move in a positive direction?" etc.
Try this out:
func splitByMissingInteger(array: [Int]) -> [[Int]]? {
var arrayFinal :[[Int]] = [ [Int]() ]
var i = 0
for num in array{
if arrayFinal[i].isEmpty || (arrayFinal[i].last == nil){
arrayFinal[i].append(num)
} else if num == (arrayFinal[i].last! + 1){
arrayFinal[i].append(num)
} else {
i += 1
arrayFinal.append([Int]())
arrayFinal[i].append(num)
}
}
return arrayFinal
}

Answer 2

You can just sort your array and iterate them in order. Check if the element minus one is equal to the last element of your 2D array, if true append otherwise append a new array with the element and increase the index of the subarrays:
extension Collection where Element == Int {
func grouped() -> [[Element]] {
let elements = Set(self).sorted()
guard let first = elements.first else { return [] }
var result = [[first]]
var i = 0
for element in elements.dropFirst() {
if element-1 == result[i].last! {
result[i].append(element)
} else {
result.append([element])
i += 1
}
}
return result
}
}
let myArray = [0,1,2,4,7,8]
let grouped = myArray.grouped() // [[0, 1, 2], [4], [7, 8]]