1207. Unique Number of Occurrences

Problem

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&nbsp;<= 1000

• -1000 <= arr[i] <= 1000

Solution (Java)

class Solution {
    public boolean uniqueOccurrences(int[] arr) {
        Map<Integer, Integer> map = new HashMap<>();
        for (int j : arr) {
            if (map.containsKey(j)) {
                map.put(j, map.get(j) + 1);
            } else {
                map.put(j, 1);
            }
        }
        // map for check unique number of count
        Map<Integer, Integer> uni = new HashMap<>();
        for (Integer val : map.values()) {
            if (uni.containsKey(val)) {
                return false;
            } else {
                uni.put(val, 1);
            }
        }
        return true;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).