All programming languages you’re likely to use will include arithmetic operators like +, -, and *.

Let’s pretend Python left out the multiplication, *, operator.

How could we implement it ourselves? Well, multiplication is repeated addition. We can use a loop!

Here’s an iterative approach:

def multiplication(num_1, num_2):
  result = 0
  for count in range(0, num_2):
    result += num_1
  return result

multiplication(3, 7)
# 21
multiplication(5, 5)
# 25
multiplication(0, 4)
# 0

This implementation isn’t quite as robust as the built-in operator. It won’t work with negative numbers, for example. We don’t expect your implementation to handle negative numbers either!

What is the big O runtime of our implementation?