leetcode: 66. Plus One

# Given a non-negative integer represented as a non-empty array of digits, 
# plus one to the integer.
#
# You may assume the integer do not contain any leading zero, except the number 0 itself.
#
# The digits are stored such that the most significant digit is at the head of the list.

class Solution():
    def plusOne(self, x):
        x = [str(x) for x in x]
        num = int(''.join(x)) + 1
        return [int(x) for x in str(num)]


if __name__ == "__main__":
    assert Solution().plusOne([9, 9, 9, 9]) == [1, 0, 0, 0, 0]