Leetcode #788: Rotated Digits

func rotatedDigits(_ N: Int) -> Int {
    var count = 0
    for i in stride(from: 1, through: N, by: 1) {
        var num = i
        var validCount = 0
        while num > 1 {
            let digit = num % 10
            num /= 10
            if digit == 0 || digit == 1 || digit == 8 {
                continue
            }
            if digit == 2 || digit == 5 || digit == 6 || digit == 9 {
                validCount += 1
            } else {
                validCount = 0
                break
            }
        }
        if validCount > 0 {
            count += 1
        }
    }
    return count
}