Recursive Digit Sum Problem

We define super digit of an integer n using the following rules:
Given an integer, we need to find the super digit of the integer n.
If n has only 1 digit, then its super digit is n.
Otherwise, the super digit of n is equal to the super digit of the sum of the digits of n.

superDigit has the following parameter(s):

string n: a string representation of an integer
int k: the times to concatenate n to make p.

Input

The first line contains two space separated integers, n and k.

Constraints:

1 <= n <= 10^100000
1 <= k <= 100000

Output

In a new line, print the the super digit of n repeated k times.

Example

Input:

148 3

Output:

3

Explanation:

Here n=148 and k=3 , so p=148148148.

super_digit(p) = super_digit(148148148) 
               = super_digit(1+4+8+1+4+8+1+4+8)
               = super_digit(39)
               = super_digit(3+9)
               = super_digit(12)
               = super_digit(1+2)
               = super_digit(3)
               = 3

Solution of Recursive Digit Sum Problem :–

import java.util.*;
import java.lang.*;
import java.io.*;

public class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
		//your code here
      Scanner sc=new Scanner(System.in);
      int t=sc.nextInt();
      for(int j=1;j<=t;j++)
        {
          int n=sc.nextInt();
          int[] arr=new int[n];
          for(int i=0;i<n;i++)
            {
              arr[i]=sc.nextInt();
            }
          System.out.print("Case "+j+": "+sum(arr,n)+"\n");
        }
	}
  public static int sum(int[] arr,int n)
  {
    if(n<=0)
    {
      return 0;
    }  
    return (sum(arr,n-1)+arr[n-1]);
  }
}