LeetCode No.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.

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題目鏈接：https://leetcode.com/problems/add-digits/

題目大意：計算num各個位的數字之和，直到最終結果是一位數。

思路：遞歸計算。

參考代碼：

class Solution {
public:
    int addDigits(int num) {
        if ( num < 10 )
            return num ;
        int ans = 0 ;
        while ( num )
        {
            ans += ( num % 10 ) ;
            num /= 10 ;
        }
        return addDigits ( ans ) ;
    }
};