Implementation for the LeetCode problem 'Top K frequent words' solved with an hash table and min-heap

Top-frequent-word.cs

public class Solution 
{
    public IList<string> TopKFrequent(string[] words, int k) {
        var output = new string[k];
        
        if (words == null || words.Length == 0)
        {
            return output;
        }
        
        var wordFrequencyMap = new Dictionary<string, int>();
        
        foreach (string word in words)
        {
            if (wordFrequencyMap.ContainsKey(word))
            {
                wordFrequencyMap[word]++;
            }
            else
            {
                wordFrequencyMap.Add(word, 1);
            }
        }
                
        var heap = new SortedSet<(int frequency, string word)>(new WordFrequencyComparer());
        
        foreach (var pair in wordFrequencyMap)
        {
            heap.Add((pair.Value * -1, pair.Key));
        }
        
        int idx = 0;
        foreach (var pair in heap)
        {
            if (idx == k)
            {
                break;
            }
            
            output[idx] = pair.word;
            idx++;
        }
                
        return output;
    }
}

public class WordFrequencyComparer : IComparer<(int frequency, string word)>
{
    public int Compare((int frequency, string word) firstWordFrequency, (int frequency, string word) secondWordFrequency)
    {
        if (firstWordFrequency.frequency == secondWordFrequency.frequency)
        {
            return firstWordFrequency.word.CompareTo(secondWordFrequency.word);
        }
        
        return firstWordFrequency.frequency - secondWordFrequency.frequency;
    }
}