leetcode 1523. Count Odd Numbers in an Interval Range

https://leetcode.com/problems/count-odd-numbers-in-an-interval-range/description/

Count Odd Numbers in an Interval Range - LeetCode

 

class Solution:
    def countOdds(self, low: int, high: int) -> int:
        if low%2 == 0 and high % 2 == 0 : 
            answer = (high-low)//2
        else:
            answer = (high-low)//2 + 1
 
        return answer

사실 이 문제는 공학적으로 생각하기보단.. 수학(정수론) 적으로 생각하면 되게 쉽게 풀려요

low와 high가 둘다 짝수일 때와 아닐경우 생각해보세요!

In fact, this problem is solved very easily if you think mathematically (number theory) rather than engineering.
Think about when low and high are both even and when they are not!