LeetCode 之 Add Digits
Given a non-negative integer num, repeatedly add all its digits until the result has onlyone digit.For example:Given num = 38, the process is like: 3+ 8 = 11, 1 + 1 = 2. Since 2 hason
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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.
Follow up:
Could you do it without any loop/recursion in O(1) runtime?
LeetCode前面的题都比较简单，有几个是关于数字规律的，如果能找到的话，很快就能解决，难度不在代码上的。最基本的方法是列举法从0到30我们就能很确定规律了：ans是以9为周期的，所以代码如下：
class Solution {
public:
int addDigits(int num) {
return (num-1)%9+1;
}
};
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