01207_unique_number_of_occurrences

Unique Number of Occurrences

Link to Problem: 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.

Examples

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

Thoughts

I've done a couple of hash table problems at this point, so it was actually easy to write the solution for this.

I have learned a few new things that I could probably use in future problems.

First is Map.values/1 which is a convenience function to convert all values of a map into a list.

Second is the MapSet data structure which I honestly have forgotten is a thing. It's Elixir's Hash Set and, as expected in most programming languages, can only contain unique elements inside it.