Sum of Single Input in Recursion Function

[PopRockCandy]

Lets say I have a single input of the value 5432. I want these values to be added together like this:

  5 + 4 + 3 + 2 = 14

What are the different ways you can code this in a recursion function? So far I've thought about populating an array, but I believe it has to be a single input. What I had in mind would require 4 inputs to populate the array.

Another way was to convert string to int but I'm not sure if I could do it due the single input problem.

[LA48b7Xj]

#include <iostream>
using namespace std;

int sum_digits(int n)
{
    if(!n)
        return 0;

    return sum_digits(n/10) + n%10;
}

int main()
{
    cout << sum_digits(5432) << '\n';
}