Python Beginner Algorithms Tutorial

# Subtract the Product and Sum of Digits of an Integer (via Leetcode)

Problem setup:

This problem can be found on Leetcode.

Given an integer number n, return the difference between the product of its digits and the sum of its digits.

### Test Cases¶

In :
# assert subtract_product_and_sum(35) == 27

• Product of digits = 3 * 5 = 35
• Sum of digits = 3 + 5 = 8
• Difference = 35 - 8 = 27
In :
# assert subtract_product_and_sum(235) == 20

• Product of digits = 2 3 5 = 30
• Sum of digits = 2 + 3 + 5 = 10
• Difference = 30 - 10 = 20

### Pseudocode¶

In [ ]:
# define function to with argument for num
# cast num to a string to be able to iterate over its digits
# assign variable to hold product of digits as 1
# assign variable to hold sum of digits as 0

# iterate over each digit in string version of number:
# cast string digit to an integer
# product of digits = product of digits * integer digit
# sum of digits = sum of digits * integer digit
# assign variable difference to be product of digits minus sum of digits
# return difference


My solution above is the simplest possible solution. I wouldn't dwell on space and time complexity here. There's minimal space used as only 3 variables are created (no data structures). For time complexity, the simplest possible operation is done which is a single iteration over each digit in the input integer.

### Code¶

In :
def subtract_product_and_sum(n)
str_n = str(n)
product_of_digits = 1
sum_of_digits = 0
for number in str_n:
int_n = int(number)
product_of_digits *= int_n
sum_of_digits += int_n
diff = product_of_digits - sum_of_digits
return diff


### Verify test cases¶

In [ ]:
assert subtract_product_and_sum(35) == 27

In [ ]:
assert subtract_product_and_sum(235) == 20