# [258. Add Digits](https://leetcode.com/problems/add-digits/description/) # 思路 没什么好说的,按照题目的意思,用两个while循环即可。 # C++ ``` C++ class Solution { public: int addDigits(int num) { int res = 0; while(num >= 10){ while(num > 0){ res += (num % 10); num /= 10; } num = res; res = 0; } return num; } }; ```