我应该从这段代码中改变什么

Question

I want to make a program to count the sum of digits in a string but only using stdio.h but the program needs to count until its less than 10 so the example you input 56 it would be 5+6=11 then 1+1=2 and so on

here's my code. For now I'm just confused how to check if its whether more than 9 or not

#include<stdio.h>

int plus(int n);
int main(void)
{
    int n, digit, test;
    scanf("%d", &n);
    test = plus(n);
    while(test != 0)
    {
        if(test > 9)
            plus(test);
        else
            break;  
    }
    printf("%d", test);
}

int plus(int n)
{
    int digit=0,test=0;
    while(n != 0)
    {
        digit = n%10;
        test = test + digit;
        n = n/10;       
    }
    return test;
}

Answer 1

You are not storing the value returned by plus function in the while body.

You can change the condition in while to check whether it is greater than 9 or not, and assign test as test = plus(test);

So, your while will look like this.

while(test > 9)
{
    test=plus(test);
}

Answer 2

You need to recursively call the function plus() until the value returned by it becomes less than 10. Like shown below:

int main(void)
 {
    int n=56;
    while(n> 10)
    {
      n = plus(n);
    }
    printf("%d", n);
}