solution.py

# Your task is to create a function called sum_arrays() in Python or addArrays in Javascript,
# which takes two arrays consisting of integers, and returns the sum of those two arrays.

# The twist is that (for example) [3,2,9] does not equal 3 + 2 + 9, it would equal '3' + '2' + '9'
# converted to an integer for this kata, meaning it would equal 329.
# The output should be an array of the the sum in a similar fashion to the input
# (for example, if the sum is 341, you would return [3,4,1]).
# Examples are given below of what two arrays should return.

# [3,2,9],[1,2] --> [3,4,1]
# [4,7,3],[1,2,3] --> [5,9,6]
# [1],[5,7,6] --> [5,7,7]
# If both arrays are empty, return an empty array.

# In some cases, there will be an array containing a negative number as the first index in the array. In this case treat the whole number as a negative number. See below:

# [3,2,6,6],[-7,2,2,8] --> [-3,9,6,2] # 3266 + (-7228) = -3962


def sum_arrays(array1, array2):
    if not array1 + array2:
        return []

    array1 = 0 if not array1 else int(''.join(list(map(str, array1))))
    array2 = 0 if not array2 else int(''.join(list(map(str, array2))))
    s = array1 + array2

    lst = list(map(int, str(abs(s))))
    if s < 0:
        lst[0] = -lst[0]

    return lst