66.加一

class Solution:
    def plusOne(self, digits: List[int]) -> List[int]:
        for i in reversed(range(len(digits))):
            if digits[i] == 9:
                digits[i] = 0
            else:
                digits[i] += 1
                return digits
        digits[0] = 1
        digits.append(0)
        return digits