findUniqueOccurances.java

class Solution {
    public boolean uniqueOccurrences(int[] arr) {
        Arrays.sort(arr);
        var seen = new HashMap<Integer, List<Integer>>();
        var s = 0;
        var e = 0;
        var len = arr.length;
        while (e < len){

            while ( e < len && arr[s] == arr[e]){
                e++;
            }
            var key = (e-s);
            var values = seen.getOrDefault(key, new ArrayList<Integer>());
            if (!values.isEmpty()){
                return false;
            }
            values.add(arr[s]);
            seen.put(key, values);
            s = e;
            
        }
        return true;
    }
}

Leet code

Link of the question here

Achievement

The code submitted beats 97% of the total submissions in terms of runtime with 2 ms as runtime and beats 21% of total submissions in terms of space complexity.