Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.
For example:
Given num = 38, the process is like: 3 + 8 = 11, 1 + 1 = 2. Since 2 has only one digit, return it.

public class Solution {
    public int addDigits(int num) {
        if(num <10) { 
            return num; 
        }
        int t=0;
        while(num>=1){
           t+=num%10;
           num=num/10;
        }
        return addDigits(t);
     }
 }

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