The Interview Question Today#4(27-2-19)

Question:

Compute the sum of digits in all number from 1 to n.

Example:

Input: n = 10

Output:

Enter the Upper Limit 10

Sum of digits in numbers from 1 to 10 is 46

Solution:

Approach:

The solution is to go through every number x from 1 to n, and compute sum in x by traversing all digits of x. 

C program:

#include<stdio.h>

int sumOfDigits(int );

int sumOfDigitsFrom1ToN(int n)

{

    int result = 0; // initialize result

int x;

    for ( x = 1; x <= n; x++)

        result += sumOfDigits(x);

    return result;

}

int sumOfDigits(int x)

{

    int sum = 0;

    while (x != 0)

    {

        sum += x %10;

        x   = x /10;

    }

    return sum;

}

int main()

{

    int n;

    printf("Enter the Upper Limit");

    scanf("%d",&n);

    printf("Sum of digits in numbers from 1 to %d is %d",n,sumOfDigitsFrom1ToN(n));

    return 0;

}

Output:

Enter the Upper Limit 10

Sum of digits in numbers from 1 to 10 is 46