// Find the first number greater than given, made up with the same digits
// 0 - lowest digit in input array of digits
func nextNumber(digits: [Int]) -> [Int]
{
    var next = digits
    for i in 1..<next.count
    {
        if next[i] < next[i-1] // First descending order
        {
            // Find the first greater than next[i]
            var replaceIndex = i-1
            for j in 0..<i-1
            {
                if next[j] > next[i]
                {
                    replaceIndex = j
                    break
                }
            }
            swap(&next[i], &next[replaceIndex])

            // Reverse order of the remaining digits
            var left = i-1
            var right = 0
            while left > right
            {
                swap(&next[left--], &next[right++])
            }
            break
        }
    }
    return next
}