Added the implementation of Huffman coding in cpp

Author: harshendram

CPP/algorithms/greedy_algorithms/huffman_algo.cpp

@@ -0,0 +1,84 @@
+#include <iostream>
+#include <string>
+#include <queue>
+#include <vector>
+#include <map>
+
+using namespace std;
+
+struct MinHeapNode
+{
+    char data;
+    unsigned freq;
+    MinHeapNode *left, *right;
+
+    MinHeapNode(char data, unsigned freq)
+    {
+        left = right = nullptr;
+        this->data = data;
+        this->freq = freq;
+    }
+};
+
+struct compare
+{
+    bool operator()(MinHeapNode *l, MinHeapNode *r)
+    {
+        return (l->freq > r->freq);
+    }
+};
+
+void printCodes(struct MinHeapNode *root, string str)
+{
+    if (!root)
+        return;
+
+    if (root->data != '$')
+        cout << root->data << ": " << str << "\n";
+
+    printCodes(root->left, str + "0");
+    printCodes(root->right, str + "1");
+}
+
+void HuffmanCodes(string text)
+{
+    map<char, unsigned> freq;
+    for (char c : text)
+    {
+        freq[c]++;
+    }
+
+    priority_queue<MinHeapNode *, vector<MinHeapNode *>, compare> minHeap;
+
+    for (auto pair : freq)
+    {
+        minHeap.push(new MinHeapNode(pair.first, pair.second));
+    }
+
+    MinHeapNode *left, *right, *top;
+
+    while (minHeap.size() != 1)
+    {
+        left = minHeap.top();
+        minHeap.pop();
+
+        right = minHeap.top();
+        minHeap.pop();
+
+        top = new MinHeapNode('$', left->freq + right->freq);
+        top->left = left;
+        top->right = right;
+
+        minHeap.push(top);
+    }
+
+    cout << "Huffman Codes for the text:\n";
+    printCodes(minHeap.top(), "");
+}
+
+int main()
+{
+    string str = "huffman coding is a greedy algorithm";
+    HuffmanCodes(str);
+    return 0;
+}