Sum of digits as string

C program to find sum of digits of a number taken as a string #

This C program will find the sum of digits of a number taken as a string.

Algorithm #

1. We begin with asking the user to enter the string (here a number which we'll accept as a string).
2. Then we extract every character from the string and while finding its value as a digit, we add it to the sum.
3. We return the sum.

Problem description #

Given a string, find the sum of digits of the string.

Methods used #

• int sum(char*) - This function will find the sum of digits of the string.

Approach #

1. Take the string as input.
2. Store the string in a variable.
3. Inside for loop, take the string and extract every character and while finding its value as a digit, add it to the sum.
4. If the character is not a digit, then we ignore it.
5. If the character is a digit, then we add it to the sum.
6. Return the sum.
7. Print the sum.

Examples #

Input: 82346y8d83 Output: 32

Input: de29382h Output: 24

Input: 32378 Output: 23

Program/Source code #

/* C program to find sum of digits of a number taken as a string */

#include <stdio.h>
#include <string.h>

int sum(char *str)
{
    int sum = 0;
    size_t i;
    size_t l = strlen(str);
    for (i = 0; i < l; i++) {
        if (str[i] >= '0' && str[i] <= '9') {
            sum = sum + (str[i] - '0');
        }
    }
    return sum;
}

int main(void)
{
    char str[100];
    printf("Enter the string: ");
    scanf("%s", str);
    printf("The sum of digits of numbers in the string is: %d", sum(str));
    return 0;
}

Explanation #

The program begins with asking the user to enter the string. The string is stored in a variable str and then passed to the function sum().

In the function sum(), we begin with initializing the variable sum to 0. Then we extract every character from the string and while finding its value as a digit, we add it to the sum. If the character is not a digit, then we ignore it. If the character is a digit, then we add it to the sum and finally we return the sum.

Output #

> ./sum-of-dig-str 
Enter the string: 371638
The sum of digits of the string is: 28

> ./sum-of-dig-str
Enter the string: 98317hsxiwq98
The sum of digits of the string is: 45