Add Digits

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
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//
class Solution {
public:
    int addDigits(int num) {
        while((num/10)>0){
            int sum=0;
            while(num>0){
                int rem=num%10;
                sum=sum+rem;
                num=num/10;
            }
            num=sum;
        }
        return num;
    }
};