notes/OJ notes/pages/Leetcode Count-Odd-Numbers-in-an-Interval-Range.md

Leetcode Count-Odd-Numbers-in-an-Interval-Range

2022-07-23 15:09

Algorithms:

#algorithm #math

Difficulty:

#coding_problem #difficulty-easy

Additional tags:

#leetcode

Revisions:

N/A

Related topics:

Links:

• Link to problem

---

Problem

Given two non-negative integers low and high. Return the count of odd numbers between low and high (inclusive).

Examples

Example 1:

Input: low = 3, high = 7 Output: 3 Explanation: The odd numbers between 3 and 7 are [3,5,7].

Example 2:

Input: low = 8, high = 10 Output: 1 Explanation: The odd numbers between 8 and 10 are [9].

Constraints

• 0 <= low <= high <= 10^9

Thoughts

[!summary] This is a #math problem.

The problem is intended to be solved with math.

The key to find the solution is by analyzing and find common rules.

Solution

class Solution {
public:
  int countOdds(int low, int high) {
    return ((low % 2) | (high % 2)) + (high - low) / 2;
  }
};