258. 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.

Answer with Python:

class Solution(object):
def addDigits(self, num):
if num==0:
return 0
else:
return 1+(num -1)%9

Answer with C:

int addDigits(int num) {
return 1 + (num-1) % 9;
}