# 1207. Unique Number of Occurrences

<https://leetcode.com/problems/unique-number-of-occurrences>

## Description

Given an array of integers `arr`, return `true` if the number of occurrences of each value in the array is **unique**, or `false` otherwise.

**Example 1:**

```
**Input:** arr = [1,2,2,1,1,3]
**Output:** true
**Explanation:** The value 1 has 3 occurrences, 2 has 2 and 3 has 1. No two values have the same number of occurrences.
```

**Example 2:**

```
**Input:** arr = [1,2]
**Output:** false
```

**Example 3:**

```
**Input:** arr = [-3,0,1,-3,1,1,1,-3,10,0]
**Output:** true
```

**Constraints:**

* `1 <= arr.length <= 1000`
* `-1000 <= arr[i] <= 1000`

## ac

```java
```