Huffman Coding using greedy algorithm.

Huffman Coding/huffman.js

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+
+
+// node class is the basic structure
+// of each node present in the Huffman - tree.
+class HuffmanNode
+{
+	constructor()
+	{
+		this.data = 0;
+		this.c = '';
+		this.left = this.right = null;
+	}
+}
+
+// recursive function to print the
+	// huffman-code through the tree traversal.
+	// Here s is the huffman - code generated.
+	function printCode(root,s)
+	{
+		// base case; if the left and right are null
+		// then its a leaf node and we print
+		// the code s generated by traversing the tree.
+		if (root.left == null
+			&& root.right == null
+			&& (root.c).toLowerCase() != (root.c).toUpperCase()) {
+
+			// c is the character in the node
+			document.write(root.c + ":" + s+"<br>");
+
+			return;
+		}
+
+		// if we go to left then add "0" to the code.
+		// if we go to the right add"1" to the code.
+
+		// recursive calls for left and
+		// right sub-tree of the generated tree.
+		printCode(root.left, s + "0");
+		printCode(root.right, s + "1");
+	}
+	
+// main function
+// number of characters.
+		let n = 6;
+		let charArray = [ 'a', 'b', 'c', 'd', 'e', 'f' ];
+		let charfreq = [ 5, 9, 12, 13, 16, 45 ];
+
+		// creating a priority queue q.
+		// makes a min-priority queue(min-heap).
+		let q = [];
+
+		for (let i = 0; i < n; i++) {
+
+			// creating a Huffman node object
+			// and add it to the priority queue.
+			let hn = new HuffmanNode();
+
+			hn.c = charArray[i];
+			hn.data = charfreq[i];
+
+			hn.left = null;
+			hn.right = null;
+
+			// add functions adds
+			// the huffman node to the queue.
+			q.push(hn);
+		}
+
+		// create a root node
+		let root = null;
+		q.sort(function(a,b){return a.data-b.data;});
+		
+		// Here we will extract the two minimum value
+		// from the heap each time until
+		// its size reduces to 1, extract until
+		// all the nodes are extracted.
+		while (q.length > 1) {
+
+			// first min extract.
+			let x = q[0];
+			q.shift();
+
+			// second min extract.
+			let y = q[0];
+			q.shift();
+
+			// new node f which is equal
+			let f = new HuffmanNode();
+
+			// to the sum of the frequency of the two nodes
+			// assigning values to the f node.
+			f.data = x.data + y.data;
+			f.c = '-';
+
+			// first extracted node as left child.
+			f.left = x;
+
+			// second extracted node as the right child.
+			f.right = y;
+
+			// marking the f node as the root node.
+			root = f;
+
+			// add this node to the priority-queue.
+			q.push(f);
+			q.sort(function(a,b){return a.data-b.data;});
+		}
+
+		// print the codes by traversing the tree
+		printCode(root, "");
+
+// This code is contributed by avanitrachhadiya2155
+