Example: Summing Up Digits

Let's practice the do-while loop with the following exercise:

Sum up the digits of a positive integer n. Examples:

  • If n = 5634, the result will be: 5 + 6 + 3 + 4 = 18.
  • If n = 920, the result will be: 9 + 2 + 0 = 11.

Video: Sum of Digits

Watch this video lesson to learn how to sum the digits of given integer: https://youtu.be/sbzlzdoEbFc.

Hints and Guidelines

We can use the following idea to solve the problem: extract many times the last digit from the input number and sum the extracted digits until the input number reaches 0. Example:

  • sum = 0
  • n = 5634 🡒 extract 4; sum += 4; n = 563
  • n = 563 🡒 extract 3; sum += 3; n = 56
  • n = 56 🡒 extract 6; sum += 6; n = 5
  • n = 5 🡒 extract 5; sum += 5; n = 0 🡒 end

In more detail the above idea looks like this:

  • We create the variable n, to which we assign a value equal to the number entered by the user.
  • We create a second variable – sum, which initial value is 0. We will use it for the calculation and storage of the result.
  • As a loop condition, we will use n > 0 because after each calculation of the result in the body of the loop, we will remove the last digit of n.
  • In the body of the loop:
    • We assign a new value of sum that is the result of the sum of the current value of sum with the last digit of n.
    • We assign a new value to n, which is the result of removing the last digit of n.
  • Outside the body of the loop, we print the final value of the sum.

n % 10: returns the last digit of the number n.
n / 10: deletes the last digit of n.

Testing in the Judge System

Test your solution here: https://judge.softuni.org/Contests/Practice/Index/514#8.

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