in swift

I am getting failed in test case 6,7,8. Any help and suggestion would be appreciated

import Foundation

var arr: [[Int]] = [[0], [1]]

func calculateNumber(number: Int) -> Int {
    if arr.count > number {
            return arr[number].count
    }

    var array = [Int]()

    let from = number > 9 ? 9 : number
    for i in stride(from: from, through: 0, by: -1) where (number - i) % 2 == 0 {
            let extraNumber = (number - i) / 2
            if arr.count > extraNumber {
                    for a in arr[extraNumber] {
                            array.append(a * 10 + i)
                    }
            }
    }

    array.sort()
    array.reversed()
    arr.append(array)
    return array.count
}

func decibinaryNumbers(x: Int) -> Int {
    var prevLength = 0
    var length = 0
    var i = 0
    while true {
            length += calculateNumber(number: i)
            if length >= x {
                    break
            }
            i += 1
            prevLength = length
    }

    let index = x - prevLength - 1
    return arr[i][index]
}

let q = Int(readLine()!)!

for _ in 1...q {
    let x = Int(readLine()!)!
    print(decibinaryNumbers(x: x))
}