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527. In a number, add digits until it becomes a single digit
Write a program to add the digits of the given number until the number becomes a single digit number.
This problem is also known as Find the Single Digit Sum of a Number
Example:
Input: 256, Output: 4 256 > 13 > 4 Input: 15, Output: 6 15 > 6 Input: 82, Output: 1 82 > 10 > 1 Input: 242239, Output: 4 242239 > 22 > 4
Approach:
In this article, we are using recursion which can be easily modified to an iterative solution. I start with the given input number and find the sum of all its digits and make a recursive call with the input equal to the sum. Base cases is:
 When the input number is less than 10 then return the number.
Output:
Input: 256, Output: 4 Input: 15, Output: 6 Input: 82, Output: 1 Input: 242239, Output: 4