Thread: Sum till a Single Digit

Mathematically speaking, it's pretty awesome. I would consider a recursive function only you wrote that you have not learned functions yet, so...

whether this is optimum or some better program can be written.

perhaps...

Code:

#include <stdio.h>

int main() {
    int num, r, sum=0;
    printf("Enter a no: ");
    scanf("%d",&num);
    while( num != 0 ) {
        r = num % 10;
        num /= 10;
        sum += r;
        if ((num == 0) && (sum > 9)) {
            num = sum;
            sum = 0;
        };
    };
    printf("the sum of digits is %d",sum);
    return 0;
};