C++ Digit Sum Problem Recursive and Iterative Tutorial

Problem:

Give a Positive Integer number, find the sum of all of its digits. In Mathematics Digit Sum problems is defined as the digit sum of a natural number that is the sum of all of its digits.

Video Tutorial – Digit Sum Problem

Iterative Algorithm:

Declare a variable called sum to accumulate the sum of digits.
Initialize the variable to zero.
Loop until the number is greater than zero.
Take Modulus of the number with 10 to extract digit
Add the digit to the variable sum
Divide the number by 10 to remove the digit taken in step 5
Repeat until the number becomes zero.
The variable sum will have the sum of all the digits of the number.

Recursive Algorithm:

Base Case: If the number is Zero return 0.
Take Modulus of number by 10 to extract its digit.
Divide the number by 10 to remove the digit taken in Step 2.
Return the Method with result from step 3 + the digit.
Once Recursive calls end, you will have the result sum of Digits.

Example:

Example:
Number: 12345
Answer: 15

Code:

main.cpp

/**********************************************************
* Problem: Digit Sum Problem
*
* Programmer: CodingHelpLine
* Website: https://codinghelpline.org
*
* Description:
* Digit Sum is a mathematical problem that states given a
* natural number, the digit sum stands for the sum of all
* the digits of the given number
*
* Example: 12345
* Digit Sum => 5 + 4 + 3 + 2 + 1 => 15
*
**********************************************************/
#include <iostream>

using std::cout;
using std::endl;

// Function prototypes.

// 1. Iterative Function.
int digitSumIterative(int n);

// 2. Recursive Function
int digitSumRecursive(int n);

int main() {

int n = 12345; // => 15

// call iterative
cout << "Sum of Digits of " << n << " = " << digitSumIterative(n) << endl;

// call Recursive
cout << "Sum of Digits of " << n << " = " << digitSumRecursive(n) << endl;

return EXIT_SUCCESS;
}

// 1. Iterative Function.
// a. declare sum variable, initialize to zero
// b. loop until n > 0
// c. Take modulus
// d. Add to sum
// e. divide n by 10
// repeat until n > 0
int digitSumIterative(int n)
{
int sum = 0;

while(n > 0)
{
int digit = n % 10;
sum += digit;
n = n / 10;
}

return sum;
}

// 2. Recursive Function
int digitSumRecursive(int n)
{
// 1. Base Case
if(n == 0)
{
return 0;
}

// 2. Recursive takes these calculations
// extract digit
// divide n by 10
// call recursive method
int digit = n % 10;
n = n / 10;

return digit + digitSumRecursive(n);
}