Unique number of Occurrences

Jin Shang bio photo By Jin Shang

Given an array of integers arr, write a function that returns true if and only if the number of occurrences of each value in the array is unique.

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

Solution:

Simulation

class Solution {
public:
    bool uniqueOccurrences(vector<int>& arr) {
        map<int,int> cnt;
        set<int> app;
        for(int a: arr){
            cnt[a]++;
        }
        for(pair<const int,int> p: cnt){
            if(app.find(p.second) != app.end()){
                return false;
            }
            app.insert(p.second);
        }
        return true;
        
    }
};