# Recursive sum of digits of a number formed by repeated appends in C++

C++Server Side ProgrammingProgramming

Given two integers ‘number’ and ‘repeat’ as input. The goal is to calculate the sum of digits of the input number repeated ‘repeat’ number of times until the sum becomes a single digit. Do this till the obtained number with sum of digits becomes a single digit number. If the input number is 123 and repeat=2 than the sum of digits of 123123 will be 1+2+3+1+2+3=12 which is not a single digit number. Now the sum of digits of 12 is 1+2=3. Output will be 3

## Let us see various input output scenarios for this

Input − number=32 repeat=3

Output − Recursive sum of digits of a number formed by repeated appends is: 6

Explanation − Sum of digits of 323232 is 3+2+3+2+3+2=15 and sum of digits of 15 is 1+5=6. 6 is a single digit number so output will be 6.

Input − number=81 repeat=4

Output − Recursive sum of digits of a number formed by repeated appends is: 9

Explanation − Sum of digits of 81818181 is 1+8+1+8+1+8+1+8=36 and sum of digits of 36 is 3+6=9. 9 is a single digit number so output will be 9.

## Approach used in the below program is as follows

• Declare two integer type variables as number and repeat. Pass the data to the function as Recursive_Sum(number, repeat).

• Inside the function as Recursive_Sum(int number, int repeat)

• Declare an integer variable as total and set it with a repeat * sum(number);

• Return call to the function as sum(total).

• Inside the function as sum(int number)

• Check IF number is 0 then return 0.

• Check IF number % 9 is 0 then return 9.

• ELSE, return number % 9

• Print the result.

## Example

#include <bits/stdc++.h>
using namespace std;
int sum(int number){
if(number == 0){
return 0;
}
if(number % 9 == 0){
return 9;
}
else{
return number % 9;
}
}
int Recursive_Sum(int number, int repeat){
int total = repeat * sum(number);
return sum(total);
}
int main(){
int number = 12;
int repeat = 4;
cout<<"Recursive sum of digits of a number formed by repeated appends is: "<<Recursive_Sum(number, repeat);
return 0;
}

## Output

If we run the above code it will generate the following Output

Recursive sum of digits of a number formed by repeated appends is: 3
Updated on 03-Nov-2021 07:36:06