# https://leetcode.com/problems/unique-number-of-occurrences/
"""
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
"""
from collections import Counter


def unique_occurrences(arr: list[int]) -> bool:
    c = Counter(arr)
    vals = c.values()
    return len(vals) == len(set(vals))
