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.
Follow up:
Could you do it without any loop/recursion in O(1) runtime?
class Solution {
public:
int addDigits(int num) {
if(num <= 9) {
return num;
}
else {
return (num % 9 == 0)?9:(num % 9);
}
}
};