plus

"""
https://leetcode.com/problems/plus-one/description/
"""


class (object):
    def plusOne(self, digits):
        """
        :type digits: List[int]
        :rtype: List[int]
        >>> s = Solution()
        >>> s.plusOne([1, 2, 3])
        [1, 2, 4]
        >>> s.plusOne([4, 3, 2 ,1])
        [4, 3, 2, 2]
        >>> s.plusOne([1, 9, 9])
        [2, 0, 0]
        >>> s.plusOne([9, 9, 9])
        [1, 0, 0, 0]
        """
        if digits == [0]:
            return [1]
        idx = len(digits) - 1
        while True:
            digits[idx] += 1
            if digits[idx] != 10:
                return digits
            else:
                digits[idx] = 0
                idx -= 1
                if idx == -1:
                    return [1] + digits