Leetcode49: Add Digits

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.

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