Given an integer num, repeatedly add all its digits until the result has only one digit, and return it.
Example 1:
Input: num = 38
Output: 2
Explanation: The process is
38 --> 3 + 8 --> 11
11 --> 1 + 1 --> 2
Since 2 has only one digit, return it.
Example 2:
Input: num = 0
Output: 0
Constraints:
- 0 <=
num<= 231 - 1
To compile java code:
$ javac nameOfFile.java will create nameOfFile.class
then
$ java nameOfFile