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

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