K Mmost Frequent Words in a File

using System;
using System.Collections.Generic;
using System.Linq;

class MainClass {
    public static void ProcessText(string text, int k) {
        
        // Store Frequencies of all words
        Dictionary<string, int> freqMap = new Dictionary<string, int>();
        string[] words = text.Split(' ');
        foreach (string word in words) {
            if (freqMap.ContainsKey(word)) {
                freqMap[word]++;
            } else {
                freqMap[word] = 1;
            }
        }

        // Store frequency map items in a priority queue 
        // (max heap) with frequency as key
        var pq = new PriorityQueue<string, int>();
        foreach (var entry in freqMap) {
            pq.Enqueue(entry.Key, -entry.Value); 
            if (pq.Count > k) pq.Dequeue();
        }

        // Get the top frequency items 
        List<KeyValuePair<string, int>> res = new List<KeyValuePair<string, int>>();
        while (pq.Count > 0) {
            var item = pq.Dequeue();
            res.Add(new KeyValuePair<string, int>(item.Item1, -item.Item2)); 
        }
        res.Reverse(); // To get the highest frequency first
        foreach (var entry in res) 
            Console.WriteLine(entry.Key + " : " + entry.Value);
    }

    public static void Main(string[] args) {
        string text = "Welcome to the world of Geeks Geeks for Geeks is great";
        ProcessText(text, 5);
    }
}

using System;
using System.IO;
using System.Collections.Generic;
using System.Text.RegularExpressions;

class Node {
    public bool isEnd;
    public int freq;
    public int ind;
    public Node[] children;

    public Node() {
        isEnd = false;
        freq = 0;
        ind = -1;
        children = new Node[26];
    }
}

class MinHeapNode {
    public Node root;
    public int freq;
    public string word;

    public MinHeapNode() {
        root = null;
        freq = 0;
        word = "";
    }
}

class MinHeap {
    public int cap;
    public int count;
    public MinHeapNode[] arr;

    public MinHeap(int cap) {
        this.cap = cap;
        count = 0;
        arr = new MinHeapNode[cap];
        for (int i = 0; i < cap; i++) {
            arr[i] = new MinHeapNode();
        }
    }

    public void SwapNodes(int a, int b) {
        MinHeapNode temp = arr[a];
        arr[a] = arr[b];
        arr[b] = temp;
        arr[a].root.ind = a;
        arr[b].root.ind = b;
    }

    public void Heapify(int idx) {
        int left = 2 * idx + 1;
        int right = 2 * idx + 2;
        int mini = idx;
        if (left < count && arr[left].freq < arr[mini].freq)
            mini = left;
        if (right < count && arr[right].freq < arr[mini].freq)
            mini = right;
        if (mini != idx) {
            SwapNodes(idx, mini);
            Heapify(mini);
        }
    }

    public void Build() {
        for (int i = (count - 1) / 2; i >= 0; --i)
            Heapify(i);
    }
}

class GfG {

    static void Insert(MinHeap mH, Node root, string word) {

        // Case 1: word is already in mH, 
        // so update its freq.
        if (root.ind != -1) {
            ++mH.arr[root.ind].freq;
            mH.Heapify(root.ind);
        }

        // Case 2: Word is not in mH and 
        // there's still room.
        else if (mH.count < mH.cap) {
            MinHeapNode node = new MinHeapNode();
            node.root = root;
            node.freq = root.freq;
            node.word = word;
            mH.arr[mH.count] = node;
            root.ind = mH.count++;
            mH.Build();
        }

        // Case 3: Heap is full and freq of new 
        // word is greater than the root.
        else if (root.freq > mH.arr[0].freq) {
            mH.arr[0].root.ind = -1;
            MinHeapNode node = new MinHeapNode();
            node.root = root;
            node.freq = root.freq;
            node.word = word;
            mH.arr[0] = node;
            root.ind = 0;
            mH.Heapify(0);
        }
    }

    static void InsertUtil(Node root, MinHeap mH, string word, int index = 0) {
        if (index < word.Length) {
            int pos = Char.ToLower(word[index]) - 'a';
            if (pos >= 0 && pos < 26) {
                if (root.children[pos] == null) {
                    root.children[pos] = new Node();
                }
                InsertUtil(root.children[pos], mH, word, index + 1);
            }
        } else {
            if (root.isEnd)
                ++root.freq;
            else {
                root.isEnd = true;
                root.freq = 1;
            }
            Insert(mH, root, word);
        }
    }

    static void InsertTrieAndHeap(string word, Node root, MinHeap mH) {
        InsertUtil(root, mH, word);
    }

    static void DisplayMinHeap(MinHeap mH) {
        for (int i = 0; i < mH.count; ++i)
            Console.WriteLine(mH.arr[i].word + " : " + mH.arr[i].freq);
    }

    static void PrintKMostFreq(StreamReader file, int k) {
        MinHeap mH = new MinHeap(k);
        Node root = new Node();

        // to process the words in file
        string line;
        while ((line = file.ReadLine()) != null) {
            foreach (string word in Regex.Split(line, @"\W+")) {
                if (!string.IsNullOrEmpty(word)) {
                    InsertTrieAndHeap(word.ToLower(), root, mH);
                }
            }
        }
        DisplayMinHeap(mH);
    }

    static void PrintKMostFreq(string str, int k) {
        MinHeap mH = new MinHeap(k);
        Node root = new Node();

        foreach (string word in Regex.Split(str, @"\W+")) {
            if (!string.IsNullOrEmpty(word)) {
                InsertTrieAndHeap(word.ToLower(), root, mH);
            }
        }

        DisplayMinHeap(mH);
    }

    public static void Main() {
        int k = 5;

        // to read from file
        // using (StreamReader file = new StreamReader("file.txt")) {
        //     PrintKMostFreq(file, k);
        // }

        // using string instead of file to 
        // test and run the code
        string str = "Welcome to the world of Geeks . This portal has been created to provide well written well thought and well explained solutions for selected questions If you like Geeks for Geeks and would like to contribute here is your chance You can write article and mail your article to contribute at geeksforgeeks org See your article appearing on the Geeks for Geeks main page and help thousands of other Geeks";
        PrintKMostFreq(str, k);
    }
}