LeetCode258. Add Digits

文章目录

• • 一、题目
  • 二、题解

一、题目

Given an integer num, repeatedly add all its digits until the result has only one digit, and return it.

Example 1:

Input: num = 38

Output: 2

Explanation: The process is

38 --> 3 + 8 --> 11

11 --> 1 + 1 --> 2

Since 2 has only one digit, return it.

Example 2:

Input: num = 0

Output: 0

Constraints:

0 <= num <= 231 - 1

Follow up: Could you do it without any loop/recursion in O(1) runtime?

二、题解

class Solution {
public:
    int addDigits(int num) {
        while(num > 9){
            int sum = 0;
            while(num){
                sum += num % 10;
                num /= 10;
            }
            num = sum;
        }
        return num;
    }
};