> For the complete documentation index, see [llms.txt](https://jaywin.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jaywin.gitbook.io/leetcode/solutions/1346-check-if-n-and-its-double-exist.md).

# 1346. Check If N and Its Double Exist

<https://leetcode.com/problems/check-if-n-and-its-double-exist>

## Description

Given an array `arr` of integers, check if there exists two integers `N` and `M` such that `N` is the double of `M` ( i.e. `N = 2 * M`).

More formally check if there exists two indices `i` and `j` such that :

* `i != j`
* `0 <= i, j < arr.length`
* `arr[i] == 2 * arr[j]`

**Example 1:**

```
**Input:** arr = [10,2,5,3]
**Output:** true
**Explanation:** N = 10 is the double of M = 5,that is, 10 = 2 * 5.
```

**Example 2:**

```
**Input:** arr = [7,1,14,11]
**Output:** true
**Explanation:** N = 14 is the double of M = 7,that is, 14 = 2 * 7.
```

**Example 3:**

```
**Input:** arr = [3,1,7,11]
**Output:** false
**Explanation:** In this case does not exist N and M, such that N = 2 * M.
```

**Constraints:**

* `2 <= arr.length <= 500`
* `-10^3 <= arr[i] <= 10^3`

## ac

```java
```