HOMEWORK $22$: Recursive Sum of Digits

Write a function that is passed a number and returns the sum of its digits using recursion. For example:

$\backslash$table$[[$Sum of Digits$],[$Sum of Digits,$]]$

input: $21$ output: $3$

input: $687$ output: $21$

I'll give you a hint on the logic. The Mod operator can be a powerful tool. Let think through an example, let's say that $n=523,$ and we have $2$ additional variables, temp and sum. This function could be easily executed with a Do$-$While Loop, but you must use recursion to get credit. $($VBA$)$

rirst pass through the recursive loop

temp $=n$ Mod $10$ 'temp $=523810=3$

sum $=$ sum $+$ temp ${\displaystyle \underset{?}{\overset{?}{}}}=0+3=3$

$n=n-$temp, $n=523-3=520$

$n=\frac{n}{10}\text{'}n=\frac{520}{10}=52$

$[$do the reqursive part$]$

$1$ second pass through the recursive loop

temp $=$nMod$10$ 'temp $=52$&$10=2$

sum $=$ sum $+$ temp ${\displaystyle \underset{?}{\overset{?}{}}}=3+2=5$

$n=n-$tempquadnn$=52-2=50$

$n=\frac{n}{\frac{?}{?}}10qua{d}^{\text{'}}n=\frac{50}{\frac{?}{?}}10=5$

$[dotherecursi]vepart$

$[$teII the code to stop nov$]$