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Sum of digits of a Number in C

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This tutorial is to find the sum of digits of a number using for loop and while loop in C. You need to have knowledge of the following topics in C.

Explanation:
To find the sum of the digits means to add all the digits present in the number. For example: consider a number 123, sum of the digits of 123 will be 1+2+3 = 6.

C Program to find the sum of the digits of a number using for loop

#include <stdio.h>

int main()
{
  int num, sum = 0, rem, i;

  printf("Enter a number: ");
  scanf("%d", &num);

  for (i = num; num != 0; num = num / 10)
  {
    rem = num % 10;
    sum = sum + rem;
  }

  printf("Sum of digits of a number: %d", sum);

  return 0;
}

Output:

Enter a number: 245
Sum of digits of a number: 11

C Program to find the sum of the digits of a number using while loop

To find the sum of a digit in c using while loop is similar to the for loop, here you need to initialize i with num after the input is taken from the user and i increment is done inside the while body as shown below.

#include <stdio.h>

int main()
{
  int num, sum = 0, rem, i;

  printf("Enter a number: ");
  scanf("%d", &num);

  i = num;

  while (num != 0)
  {
    rem = num % 10;
    sum = sum + rem;
    num = num / 10;
  }

  printf("Sum of digits of a number: %d", sum);

  return 0;
}

Output:

Enter a number: 123
Sum of digits of a number: 6

C Program to find the sum of the digits of a number using recursion function

#include <stdio.h>

int sumDigits(int);
int main()
{
  int num, result;

  printf("Enter a number: ");
  scanf("%d", &num);

  result = sumDigits(num);

  printf("Sum of digits of a number: %d", result);

  return 0;
}

int sumDigits(int n)
{
  if (n == 0)
    return 0;

  return (n % 10 + sumDigits(n / 10));	//recursion call
}

Output:

Enter a number: 123
Sum of digits of a number: 6

Learn more on recursion.

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