C++ Recursion: Implementing recursive function for sum of digits

Last update on December 20 2024 12:25:15 (UTC/GMT +8 hours)

Write a C++ program to implement a recursive function to calculate the sum of digits of a given number.

Sample Solution:

C Code:

// Recursive function to calculate the sum of digits
#include <iostream> // Including the Input/Output Stream Library

int sumOfDigits(int number) {
  // If the number is a single digit, return the number itself
  if (number >= 0 && number <= 9)
    return number;

  // Recursive case: Calculate the sum of the last digit and the sum of the rest of the digits
  return (number % 10) + sumOfDigits(number / 10);
}

int main() {
  int n;
  std::cout << "Input a number: "; // Prompting the user to input a number
  std::cin >> n; // Reading the input number from the user

  // Calculate the sum of digits using recursion
  int sum_digits = sumOfDigits(n); // Calling the recursive function to compute the sum of digits

  std::cout << "Sum of digits of " << n << " is: " << sum_digits << std::endl; // Displaying the sum of digits

  return 0; // Returning 0 to indicate successful execution of the program
}

Sample Output:

Input a number: 100
Sum of digits of 100 is: 1

Input a number: 123
Sum of digits of 123 is: 6

Input a number: 56459
Sum of digits of 56459 is: 29

Explanation:

In the above exercise,

• The sumOfDigits function takes an integer n as a parameter and calculates the sum of its digits using recursion.
• The base case is when the number is a single digit (0 to 9), in which case the function returns the number itself.
• In the recursive case, the function calculates the sum of the last digit (number % 10) and the sum of the rest of the digits (sumOfDigits(number / 10)).
• The main function prompts the user to enter a number, calculates the sum of its digits using the sumOfDigits function, and displays the result.

Flowchart:

CPP Code Editor:

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