Python Exercise:  Compute Checksum Digit for an ISBN Number
Channel: Christian Hur
Date: 15/11/2021

⭕ Overview
In this video, I guide you through a two-part exercise designed to enhance your problem-solving skills. The first part focuses on understanding the problem statement and the formula given. It's crucial to grasp what is being asked before attempting a solution. We'll break down the formula and the calculations involved, ensuring you comprehend each step.

Next, I'll demonstrate how to apply this formula practically. Even if you lack a strong math background, I'll simplify the process, making it approachable and easy to follow. This exercise aims to build your confidence in handling mathematical operations within programming contexts.

By the end of this tutorial, you'll be comfortable performing calculations and solving problems methodically, a valuable skill in any programming task.

Background Information:

The International Standard Book Number (ISBN) is a 10 digit code that uniquely specifies a book. The rightmost digit is a checksum digit which can be uniquely determined from the other 9 digits from the condition that d1 + 2*d2 + 3*d3 + ... + 10*d10 must be a multiple of 11 (here di denotes the ith digit from the right). The checksum digit d1 can be any value from 0 to 10: the ISBN convention is to use the value X to denote 10. Example: the checksum digit corresponding to 020131452 is 5 since is the only value of d1 between 0 and and 10 for which d1 + 2*2 + 3*5 + 4*4 + 5*1 + 6*3 + 7*1 + 8*0 + 9*2 + 10*0 is a multiple of 11.

Futher information:

Notice the 9-digit integer 020131452 in reverse oder:
2*2 + 3*5 + 4*4 + 5*1 + 6*3 + 7*1 + 8*0 + 9*2 + 10*0 = 83

What number between 0 and 10 should be added to 83 so that it is divisible by 11? 

Since 88 is the next number that is divisible by 11, the checksum number is 5:

88 - 83 = 5

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⭕ Chapters
  0:00 - Introduction

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