1207. Unique Number of Occurrences(Array, Hash Table)*

문제

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

풀이

class Solution {
    public boolean uniqueOccurrences(int[] arr) {
        HashMap<Integer, Integer> map = new HashMap<>();
        for(int i : arr){
            map.put(i,map.getOrDefault(i,0)+1);
        }
        HashSet<Integer> set = new HashSet<>();
        for(int i : map.values()){
            if(!set.add(i)) return false; 
        }

        return true;
    }
}