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](https://leetcode.com/problems/count-odd-numbers-in-an-interval-range/)

---

### 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

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