Find Kth smallest element in array

smallestKth.swift

func findSmallestKth(_ array: [Int], _ k: Int) -> Int {
    let pivot = array.first!
    let arraySmallerThanPivot = array.dropFirst().filter {$0 < pivot}
    let arrayLargerThanPivot = array.dropFirst().filter { $0 > pivot }
    let newArray = arraySmallerThanPivot + [Int(pivot)] + arrayLargerThanPivot
    let positionOfPivot = array.count > 1 ? arraySmallerThanPivot.count : 0
    if k-1 == positionOfPivot {
        return newArray[positionOfPivot]
    } else if k-1 > positionOfPivot {
        return findSmallestKth(arrayLargerThanPivot, k-1-positionOfPivot)
    } else {
        return findSmallestKth(arraySmallerThanPivot, k)
    }
}