sum13

# sum13 - https://codingbat.com/prob/p167025
# Return the sum of the numbers in the array, returning 0 for an empty array. Except the number 13 is very unlucky, so it does not count and numbers that come immediately after a 13 also do not count.
# sum13([1, 2, 2, 1]) = 6
# sum13([1, 1]) = 2
# sum13([1, 2, 2, 1, 13]) = 6
def sum13(nums):
  
  result = 0
  len_num = len(nums)
  if len_num <= 0:
    return result
  
  for i in range(len_num):
    result += nums[i] if not(nums[i] == 13 or (i >= 1 and nums[i-1] == 13)) else 0

  return result