leetcode/solution/0200-0299/0258.Add Digits

comments	difficulty	edit_url	tags
true	Easy	https://github.com/doocs/leetcode/edit/main/solution/0200-0299/0258.Add%20Digits/README_EN.md	Math Number Theory Simulation

258. Add Digits

中文文档

Description

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?

Solutions

Solution 1

Python3

class Solution:
    def addDigits(self, num: int) -> int:
        return 0 if num == 0 else (num - 1) % 9 + 1

Java

class Solution {
    public int addDigits(int num) {
        return (num - 1) % 9 + 1;
    }
}

C++

class Solution {
public:
    int addDigits(int num) {
        return (num - 1) % 9 + 1;
    }
};

Go

func addDigits(num int) int {
	if num == 0 {
		return 0
	}
	return (num-1)%9 + 1
}

Rust

impl Solution {
    pub fn add_digits(mut num: i32) -> i32 {
        ((num - 1) % 9) + 1
    }
}