Huffman Coding in C++.

Author: ezaznitd

Huffman_Coding.cpp

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+// C++ program for Huffman Coding 
+#include<bits/stdc++.h>
+using namespace std;
+// A Huffman tree node
+struct MinHeapNode
+{
+	// One of the input characters;
+	char data;
+	// Frequency of the character;
+	unsigned freq;
+	// Left and right child;
+	MinHeapNode *left, *right;
+	MinHeapNode(char data, unsigned freq)
+	{
+		left = right = NULL;
+		this->data = data;
+		this->freq = freq; 
+	}
+};
+// For comparison of;
+// two heap nodes (needed in min heap);
+struct compare
+{
+	bool operator()(MinHeapNode* l, MinHeapNode* r)
+	{ 
+		return (l->freq > r->freq);
+	}
+};
+// Prints huffman codes from;
+// the root of Huffman Tree;
+void printCodes(struct MinHeapNode* root, string str)
+{
+	if (!root)
+		return;
+	if (root->data != '$')
+		cout << root->data << ": " << str << endl;
+	printCodes(root->left, str + "0");
+	printCodes(root->right, str + "1");
+}
+// The main function that builds a Huffman Tree and;
+// print codes by traversing the built Huffman Tree;
+void HuffmanCodes(char data[], int freq[], int size)
+{
+	struct MinHeapNode *left, *right, *top;
+	// Create a min heap & inserts all characters of data[];
+	priority_queue<MinHeapNode*, vector<MinHeapNode*>, compare> minHeap;
+	for (int i = 0; i < size; ++i)
+		minHeap.push(new MinHeapNode(data[i], freq[i]));
+	// Iterate while size of heap doesn't become 1;
+	while (minHeap.size() != 1)
+	{
+		// Extract the two minimum;
+		// freq items from min heap;
+		left = minHeap.top();
+		minHeap.pop();
+		right = minHeap.top();
+		minHeap.pop();
+		// Create a new internal node with
+		// frequency equal to the sum of the
+		// two nodes frequencies. Make the
+		// two extracted node as left and right children
+		// of this new node. Add this node
+		// to the min heap '$' is a special value
+		// for internal nodes, not used;
+		top = new MinHeapNode('$', left->freq + right->freq);
+		top->left = left;
+		top->right = right;
+		minHeap.push(top);
+	}
+	// Print Huffman codes using;
+	// the Huffman tree built above;
+	printCodes(minHeap.top(), "");
+}
+// Driver program to test above functions;
+int main()
+{
+	char arr[] = { 'a', 'b', 'c', 'd', 'e', 'f' };
+	int freq[] = { 5, 9, 12, 13, 16, 45 };
+	int size = sizeof(arr) / sizeof(arr[0]);
+	HuffmanCodes(arr, freq, size);
+	return 0;
+}