13. Unique Number of Occurrences

The problem can be found at the following link: Question Link

My Approach

This is a straightforward question where we calculate the frequency of each element using a map. After obtaining the frequency of each element, we use a set to determine if there are any duplicate frequencies among the elements in the array arr.

Time and Auxiliary Space Complexity

• Time Complexity: O(n), as we traverse an array of size n.

• Auxiliary Space Complexity: O(n), due to the unordered_map freq and the set uniqueSet.

Code (C++)

class Solution {
public:
    bool isFrequencyUnique(int n, int arr[]) {
        unordered_map<int, int> freq;
        unordered_set<int> uniqueSet;

        for (int i = 0; i < n; ++i)
            ++freq[arr[i]];

        for (auto i : freq)
            uniqueSet.insert(i.second);

        return freq.size() == uniqueSet.size();
    }
};

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