Leetcode 258:Add Digits

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.
【题目大意】给定一个数，不断地把这个数的每个数位相加，直到这个数变成一位数
【解法】数位分离，每次分离出个位数加到原数字上，直到只剩一个数位
【AC代码】

int addDigits(int num) {
    while(num >= 10){
        num = num / 10 + num % 10; 
    }  
    return num;
}