Recursive vs. Iterative Algorithm – Q&A

For this question, we are looking at an algorithm used to implement the divisibility rule for 3 which states that:

A number is divisible by 3 if the sum of all its digits is divisible by 3.
Let’s look at the following example: is 378 divisible by 3? Here is the Python code for our recursive algorithm:

def isDivisibleByThree(n):
   sum = 0
   for digit in str(n):
     sum = sum + int(digit)
   
   if sum>=10:
     return isDivisibleByThree(sum)
   else:   
     if sum==3 or sum==6 or sum==9:
       return True
     else:
       return False
       
number = int(input("Type a number"))
if isDivisibleByThree(number)==True:
  print("This number is divisible by 3.")
else: 
  print("This number is not divisible by 3.")

Explain why the above code can be described as being a recursive algorithm? State on which line of this code does the recursion occur?

Trace this algorithm if the user enters the value 8479

Rewrite the function isDivisibleByThree() using an iterative approach instead of a recursive approach.