LeetCode #1207 Unique Number of Occurrences Solution & Explanation

public class Solution {
    public bool UniqueOccurrences(int[] arr) {
        Dictionary<int,int> dict =   new Dictionary<int,int>();

        //1.count number of occurrences of each value
        foreach(var a in arr)
        {
            if (!dict.ContainsKey(a))
            {
                dict.Add(a, 1);
            }
            else
            {
                dict[a] = dict[a]+1;
            }
        }

        //2.check if there any same number by HashSet
        HashSet<int> hSet = new HashSet<int>();
        foreach(var item in dict)
        {
            if(hSet.Contains(item.Value))
            {
                return false;
            }
            hSet.Add(item.Value);
        }

        return true;
    }
}

class Solution {
    public boolean uniqueOccurrences(int[] arr) {
        Map<Integer, Integer> dict = new HashMap<Integer, Integer>();
        //1.count number of occurrences of each value
        for(int a : arr)
        {
            if (!dict.containsKey(a))
            {
                dict.put(a, 1);
            }
            else
            {
                dict.put(a, dict.get(a)+1);
            }
        }

        //2.check if there any same number by HashSet
        HashSet<Integer> hSet = new HashSet<Integer>();
        for(int val : dict.values()) 
        {
            if(hSet.contains(val))
            {
                return false;
            }
            hSet.add(val);
        }

        return true;
    }
}