Leetcode[258] Add Digits
01 Dec 2015###Task1 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?
Hint:
A naive implementation of the above process is trivial. Could you come up with other methods?
What are all the possible results?
How do they occur, periodically or randomly?
You may find this Wikipedia article useful.
###Python
class Solution(object):
def addDigits(self, num):
"""
:type num: int
:rtype: int
"""
if num == 0:
return 0
return 9 if num % 9 == 0 else num % 9
###Java
public class Solution {
public int addDigits(int num) {
return (num - 1) % 9 + 1;
}
}
###Points 使用方法I的代码循环输出0 - 19的运行结果：
in out in out
0 0 10 1
1 1 11 2
2 2 12 3
3 3 13 4
4 4 14 5
5 5 15 6
6 6 16 7
7 7 17 8
8 8 18 9
9 9 19 1
可以发现输出与输入的关系为：
out = (in - 1) % 9 + 1