Huffman coding using priority queue

Huffman Coding

Here given code implementation process.

/*
    C Program 
    Huffman coding using priority queue
*/
#include <stdio.h>
#include <stdlib.h>

struct TreeNode
{
	int first;
	char second;
	struct TreeNode *left;
	struct TreeNode *right;
};
struct QNode
{
	struct TreeNode *n;
	struct QNode *next;
	struct QNode *prev;
};
struct PriorityQueue
{
	struct QNode *front;
	struct QNode *rear;
	int size;
};
// Returns a new tree node 
struct TreeNode *newTreeNode(int first, char second)
{
	struct TreeNode *node = (struct TreeNode *) malloc(sizeof(struct TreeNode));
	if (node == NULL)
	{
		printf("\n Memory overflow , When creating a new TreeNode");
	}
	else
	{
		node->second = second;
		node->first = first;
		node->left = NULL;
		node->right = NULL;
	}
	return node;
}
// Returns a new queue 
struct PriorityQueue *newPriorityQueue()
{
	struct PriorityQueue *q = (struct PriorityQueue *) malloc(sizeof(struct PriorityQueue));
	if (q == NULL)
	{
		printf("\n Memory overflow , When creating a new Queue");
	}
	else
	{
		q->front = NULL;
		q->rear = NULL;
		q->size = 0;
	}
	return q;
}
// Add a node into Priority queue
void enQueue(struct PriorityQueue *q, struct TreeNode *auxiliary)
{
	//Create a dynamic node
	struct QNode *node = (struct QNode *) malloc(sizeof(struct QNode));
	if (node == NULL)
	{
		printf("\n Memory overflow , When creating a new Queue Node");
	}
	else
	{
		// Set node value
		node->n = auxiliary;
		node->next = NULL;
		node->prev = NULL;
		if (q->front == NULL)
		{
			// When adding a first node of queue
			q->front = node;
			q->rear = node;
		}
		else if (q->front->n->first >= auxiliary->first)
		{
			// Add node at beginning position
			node->next = q->front;
			q->front->prev = node;
			q->front = node;
		}
		else if (q->rear->n->first <= auxiliary->first)
		{
			// Add node at last position
			node->prev = q->rear;
			q->rear->next = node;
			q->rear = node;
		}
		else
		{
			struct QNode *temp = q->front;
			// Find the location of inserting priority node
			while (temp->n->first < auxiliary->first)
			{
				temp = temp->next;
			}
			// Add node
			node->next = temp;
			node->prev = temp->prev;
			temp->prev = node;
			if (node->prev != NULL)
			{
				node->prev->next = node;
			}
		}
		q->size = q->size + 1;
	}
}
int isEmpty(struct PriorityQueue *q)
{
	if (q->size == 0)
	{
		return 1;
	}
	else
	{
		return 0;
	}
}
// Get a front element of queue
struct TreeNode *peek(struct PriorityQueue *q)
{
	if (isEmpty(q) == 1)
	{
		// When stack is empty
		return NULL;
	}
	else
	{
		return q->front->n;
	}
}
int isSize(struct PriorityQueue *q)
{
	return q->size;
}
// Remove a front node of a queue
void deQueue(struct PriorityQueue *q)
{
	if (isEmpty(q) == 0)
	{
		struct QNode *temp = q->front;
		q->front->n = NULL;
		if (q->front == q->rear)
		{
			// When queue contains only one node
			q->rear = NULL;
			q->front = NULL;
		}
		else
		{
			q->front = q->front->next;
			q->front->prev = NULL;
		}
		// Change queue size
		q->size--;
		free(temp);
	}
	else
	{
		printf("\n Empty Queue \n");
	}
}
// Print elements of queue
void printQdata(struct PriorityQueue *q)
{
	struct QNode *node = q->front;
	printf("\n Queue Element ");
	while (node != NULL)
	{
		printf("\n %d  %c", node->n->first, node->n->second);
		node = node->next;
	}
	printf("\n");
}
// Display Huffman code
void printTree(struct TreeNode *node, char result[], int n)
{
	if (node == NULL)
	{
		return;
	}
	if (node->left == NULL && node->right == NULL)
	{
		result[n] = '\0';
		printf("\n %c %s", node->second, result);
		return;
	}
	result[n] = '0';
	printTree(node->left, result, n + 1);
	result[n] = '1';
	printTree(node->right, result, n + 1);
}
// Construct Huffman Code Tree
struct TreeNode *buildHuffmanCodes(char value[], int frequency[], int n)
{
	struct PriorityQueue *q = newPriorityQueue();
	struct TreeNode *root = NULL;
	struct TreeNode *n1 = NULL;
	struct TreeNode *n2 = NULL;
	// First add all elements into priority queue
	for (int i = 0; i < n; ++i)
	{
		root = newTreeNode(frequency[i], value[i]);
		enQueue(q, root);
	}
	// printQdata(q);
	// Execute loop until the priority queue contains more than 1 node
	while (isSize(q) > 1)
	{
		// Get first smallest node  
		n1 = peek(q);
		//Remove a front element
		deQueue(q);
		// Get second smallest node
		n2 = peek(q);
		// Remove a front element
		deQueue(q);
		// Make new node using two smallest node
		root = newTreeNode(n1->first + n2->first, ' ');
		// Add new node into priority queue 
		enQueue(q, root);
		// Set left and right child
		root->left = n1;
		root->right = n2;
	}
	deQueue(q);
	return root;
}
int main(int argc, char
	const *argv[])
{
	char value[] = {
		'a' , 'b' , 'c' , 'd' , 'e' , 'f' , 'g'
	};
	int frequency[] = {
		16 , 8 , 19 , 32 , 21 , 10 , 5
	};
	int n = sizeof(frequency) / sizeof(frequency[0]);
	char result[n + 1];
	struct TreeNode *root = buildHuffmanCodes(value, frequency, n);
	printTree(root, result, 0);
	return 0;
}

Output

 e 00
 f 010
 g 0110
 b 0111
 d 10
 a 110
 c 111
/*
    Java Program 
    Implement priority queue with pair
*/
class TreeNode
{
	public int first;
	public char second;
	public TreeNode left;
	public TreeNode right;
	public TreeNode(int first, char second)
	{
		this.first = first;
		this.second = second;
		this.left = null;
		this.right = null;
	}
}
class QNode
{
	public TreeNode n;
	public QNode next;
	public QNode prev;
	public QNode(TreeNode n)
	{
		this.n = n;
		this.prev = null;
		this.next = null;
	}
}
class PriorityQueue
{
	public QNode front;
	public QNode rear;
	public int size;
	public PriorityQueue()
	{
		this.front = null;
		this.rear = null;
		this.size = 0;
	}
	// Add a node into queue Priority queue
	public void enQueue(TreeNode auxiliary)
	{
		//Create a dynamic node
		QNode node = new QNode(auxiliary);
      	node.n = auxiliary;
		if (this.front == null)
		{
			// When adding a first node of queue
			this.front = node;
			this.rear = node;
		}
		else if (this.front.n.first >= auxiliary.first)
		{
			// Add node at beginning position
			node.next = this.front;
			this.front.prev = node;
			this.front = node;
		}
		else if (this.rear.n.first <= auxiliary.first)
		{
			// Add node at last position
			node.prev = this.rear;
			this.rear.next = node;
			this.rear = node;
		}
		else
		{
			QNode temp = this.front;
			// Find the location of inserting priority node
			while (temp.n.first < auxiliary.first)
			{
				temp = temp.next;
			}
			// Add node
			node.next = temp;
			node.prev = temp.prev;
			temp.prev = node;
			if (node.prev != null)
			{
				node.prev.next = node;
			}
		}
		this.size = this.size + 1;
	}
	public boolean isEmpty()
	{
		if (this.size == 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	// Get a front element of queue
	public TreeNode peek()
	{
		if (this.isEmpty() == true)
		{
			System.out.print("\n Empty Queue \n");
			// When Queue is empty
			return null;
		}
		else
		{
			return this.front.n;
		}
	}
	public int isSize()
	{
		return this.size;
	}
	// Remove a front node of a queue
	public void deQueue()
	{
		if (this.isEmpty() == false)
		{
			QNode temp = this.front;
			if (this.front == this.rear)
			{
				// When queue contains only one node
				this.rear = null;
				this.front = null;
			}
			else
			{
				this.front = this.front.next;
				this.front.prev = null;
			}
			// Change queue size
			this.size--;
		}
	}
	// Print elements of queue
	public void printQdata()
	{
		QNode node = this.front;
		System.out.print("\n Queue Element ");
		while (node != null)
		{
			System.out.print("\n " + node.n.first + " " + node.n.second);
			node = node.next;
		}
		System.out.print("\n");
	}
}
public class HuffmanCodes
{
	// Display Huffman code
	public void printTree(TreeNode node, String result)
	{
		if (node == null)
		{
			return;
		}
		if (node.left == null && node.right == null)
		{
			System.out.print("\n " + node.second + " " + result);
			return;
		}
		printTree(node.left, result + "0");
		printTree(node.right, result + "1");
	}
	// Construct Huffman Code Tree
	public TreeNode buildHuffmanCodes(char[] value, int[] frequency, int n)
	{
		PriorityQueue q = new PriorityQueue();
		TreeNode root = null;
		TreeNode n1 = null;
		TreeNode n2 = null;
		// First add all elements into priority queue
		for (int i = 0; i < n; ++i)
		{
			root = new TreeNode(frequency[i], value[i]);
			q.enQueue(root);
		}
		// printQdata(q);
		// Execute loop until the priority queue contains more than 1 node
		while (q.isSize() > 1)
		{
			// Get first smallest node  
			n1 = q.peek();
			//Remove a front element
			q.deQueue();
			// Get second smallest node
			n2 = q.peek();
			// Remove a front element
			q.deQueue();
			// Make new node using two smallest node
			root = new TreeNode(n1.first + n2.first, ' ');
			// Add new node into priority queue 
			q.enQueue(root);
			// Set left and right child
			root.left = n1;
			root.right = n2;
		}
		q.deQueue();
		return root;
	}
	public static void main(String[] args)
	{
		HuffmanCodes task = new HuffmanCodes();
		char[] value = {
			'a' , 'b' , 'c' , 'd' , 'e' , 'f' , 'g'
		};
		int[] frequency = {
			16 , 8 , 19 , 32 , 21 , 10 , 5
		};
		int n = frequency.length;
		TreeNode root = task.buildHuffmanCodes(value, frequency, n);
		task.printTree(root, "");
	}
}

Output

 e 00
 f 010
 g 0110
 b 0111
 d 10
 a 110
 c 111
// Include header file
#include <iostream>

using namespace std;
/*
    C++ Program 
    Implement priority queue with pair
*/
class TreeNode
{
	public: 
    int first;
	char second;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int first, char second)
	{
		this->first = first;
		this->second = second;
		this->left = NULL;
		this->right = NULL;
	}
};
class QNode
{
	public: TreeNode *n;
	QNode *next;
	QNode *prev;
	QNode(TreeNode *n)
	{
		this->n = n;
		this->prev = NULL;
		this->next = NULL;
	}
};
class PriorityQueue
{
	public: QNode *front;
	QNode *rear;
	int size;
	PriorityQueue()
	{
		this->front = NULL;
		this->rear = NULL;
		this->size = 0;
	}
	// Add a node into queue Priority queue
	void enQueue(TreeNode *auxiliary)
	{
		//Create a dynamic node
		QNode *node = new QNode(auxiliary);
		node->n = auxiliary;
		if (this->front == NULL)
		{
			// When adding a first node of queue
			this->front = node;
			this->rear = node;
		}
		else if (this->front->n->first >= auxiliary->first)
		{
			// Add node at beginning position
			node->next = this->front;
			this->front->prev = node;
			this->front = node;
		}
		else if (this->rear->n->first <= auxiliary->first)
		{
			// Add node at last position
			node->prev = this->rear;
			this->rear->next = node;
			this->rear = node;
		}
		else
		{
			QNode *temp = this->front;
			// Find the location of inserting priority node
			while (temp->n->first < auxiliary->first)
			{
				temp = temp->next;
			}
			// Add node
			node->next = temp;
			node->prev = temp->prev;
			temp->prev = node;
			if (node->prev != NULL)
			{
				node->prev->next = node;
			}
		}
		this->size = this->size + 1;
	}
	bool isEmpty()
	{
		if (this->size == 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	// Get a front element of queue
	TreeNode *peek()
	{
		if (this->isEmpty() == true)
		{
			// When Queue is empty
			cout << "\n Empty Queue \n";
			return NULL;
		}
		else
		{
			return this->front->n;
		}
	}
	int isSize()
	{
		return this->size;
	}
	// Remove a front node of a queue
	void deQueue()
	{
		if (this->isEmpty() == false)
		{
			QNode *temp = this->front;
			if (this->front == this->rear)
			{
				// When queue contains only one node
				this->rear = NULL;
				this->front = NULL;
			}
			else
			{
				this->front = this->front->next;
				this->front->prev = NULL;
			}
          	temp->n = NULL;
          	delete temp;
			// Change queue size
			this->size--;
		}
	}
	// Print elements of queue
	void printQdata()
	{
		QNode *node = this->front;
		cout << "\n Queue Element ";
		while (node != NULL)
		{
			cout << "\n " << node->n->first << " " << node->n->second;
			node = node->next;
		}
		cout << "\n";
	}
};
class HuffmanCodes
{
	public:
		// Display Huffman code
		void printTree(TreeNode *node, string result)
		{
			if (node == NULL)
			{
				return;
			}
			if (node->left == NULL && node->right == NULL)
			{
				cout << "\n " << node->second << " " << result;
				return;
			}
			this->printTree(node->left, result  + "0");
			this->printTree(node->right, result + "1");
		}
	// Construct Huffman Code Tree
	TreeNode *buildHuffmanCodes(char value[], int frequency[], int n)
	{
		PriorityQueue q = PriorityQueue();
		TreeNode *root = NULL;
		TreeNode *n1 = NULL;
		TreeNode *n2 = NULL;
		// First add all elements into priority queue
		for (int i = 0; i < n; ++i)
		{
			root = new TreeNode(frequency[i], value[i]);
			q.enQueue(root);
		}
		// printQdata(q);
		// Execute loop until the priority queue contains more than 1 node
		while (q.isSize() > 1)
		{
			// Get first smallest node
			n1 = q.peek();
			//Remove a front element
			q.deQueue();
			// Get second smallest node
			n2 = q.peek();
			// Remove a front element
			q.deQueue();
			// Make new node using two smallest node
			root = new TreeNode(n1->first + n2->first, ' ');
			// Add new node into priority queue
			q.enQueue(root);
			// Set left and right child
			root->left = n1;
			root->right = n2;
		}
		q.deQueue();
		return root;
	}
};
int main()
{
	HuffmanCodes task = HuffmanCodes();
	char value[] = {
		'a' , 'b' , 'c' , 'd' , 'e' , 'f' , 'g'
	};
	int frequency[] = {
		16 , 8 , 19 , 32 , 21 , 10 , 5
	};
	int n = sizeof(frequency) / sizeof(frequency[0]);
	TreeNode *root = task.buildHuffmanCodes(value, frequency, n);
	task.printTree(root, "");
	return 0;
}

Output

 e 00
 f 010
 g 0110
 b 0111
 d 10
 a 110
 c 111
// Include namespace system
using System;
/*
    C# Program 
    Implement priority queue with pair
*/
public class TreeNode
{
	public int first;
	public char second;
	public TreeNode left;
	public TreeNode right;
	public TreeNode(int first, char second)
	{
		this.first = first;
		this.second = second;
		this.left = null;
		this.right = null;
	}
}
public class QNode
{
	public TreeNode n;
	public QNode next;
	public QNode prev;
	public QNode(TreeNode n)
	{
		this.n = n;
		this.prev = null;
		this.next = null;
	}
}
public class PriorityQueue
{
	public QNode front;
	public QNode rear;
	public int size;
	public PriorityQueue()
	{
		this.front = null;
		this.rear = null;
		this.size = 0;
	}
	// Add a node into queue Priority queue
	public void enQueue(TreeNode auxiliary)
	{
		//Create a dynamic node
		QNode node = new QNode(auxiliary);
		node.n = auxiliary;
		if (this.front == null)
		{
			// When adding a first node of queue
			this.front = node;
			this.rear = node;
		}
		else if (this.front.n.first >= auxiliary.first)
		{
			// Add node at beginning position
			node.next = this.front;
			this.front.prev = node;
			this.front = node;
		}
		else if (this.rear.n.first <= auxiliary.first)
		{
			// Add node at last position
			node.prev = this.rear;
			this.rear.next = node;
			this.rear = node;
		}
		else
		{
			QNode temp = this.front;
			// Find the location of inserting priority node
			while (temp.n.first < auxiliary.first)
			{
				temp = temp.next;
			}
			// Add node
			node.next = temp;
			node.prev = temp.prev;
			temp.prev = node;
			if (node.prev != null)
			{
				node.prev.next = node;
			}
		}
		this.size = this.size + 1;
	}
	public Boolean isEmpty()
	{
		if (this.size == 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	// Get a front element of queue
	public TreeNode peek()
	{
		if (this.isEmpty() == true)
		{
			// When Queue is empty
			Console.Write("\n Empty Queue \n");
			return null;
		}
		else
		{
			return this.front.n;
		}
	}
	public int isSize()
	{
		return this.size;
	}
	// Remove a front node of a queue
	public void deQueue()
	{
		if (this.isEmpty() == false)
		{
			QNode temp = this.front;
          	temp.n = null;
			if (this.front == this.rear)
			{
				// When queue contains only one node
				this.rear = null;
				this.front = null;
			}
			else
			{
				this.front = this.front.next;
				this.front.prev = null;
			}
           
			// Change queue size
			this.size--;
		}
	}
	// Print elements of queue
	public void printQdata()
	{
		QNode node = this.front;
		Console.Write("\n Queue Element ");
		while (node != null)
		{
			Console.Write("\n " + node.n.first + " " + node.n.second);
			node = node.next;
		}
		Console.Write("\n");
	}
}
public class HuffmanCodes
{
	// Display Huffman code
	public void printTree(TreeNode node, String result)
	{
		if (node == null)
		{
			return;
		}
		if (node.left == null && node.right == null)
		{
			Console.Write("\n " + node.second + " " + result);
			return;
		}
		printTree(node.left, result + "0");
		printTree(node.right, result + "1");
	}
	// Construct Huffman Code Tree
	public TreeNode buildHuffmanCodes(char[] value, int[] frequency, int n)
	{
		PriorityQueue q = new PriorityQueue();
		TreeNode root = null;
		TreeNode n1 = null;
		TreeNode n2 = null;
		// First add all elements into priority queue
		for (int i = 0; i < n; ++i)
		{
			root = new TreeNode(frequency[i], value[i]);
			q.enQueue(root);
		}
		// q.printQdata();
		// Execute loop until the priority queue contains more than 1 node
		while (q.isSize() > 1)
		{
			// Get first smallest node
			n1 = q.peek();
			//Remove a front element
			q.deQueue();
			// Get second smallest node
			n2 = q.peek();
			// Remove a front element
			q.deQueue();
			// Make new node using two smallest node
			root = new TreeNode(n1.first + n2.first, ' ');
			// Add new node into priority queue
			q.enQueue(root);
			// Set left and right child
			root.left = n1;
			root.right = n2;
		}
		q.deQueue();
		return root;
	}
	public static void Main(String[] args)
	{
		HuffmanCodes task = new HuffmanCodes();
		char[] value = {
			'a' , 'b' , 'c' , 'd' , 'e' , 'f' , 'g'
		};
		int[] frequency = {
			16 , 8 , 19 , 32 , 21 , 10 , 5
		};
		int n = frequency.Length;
		TreeNode root = task.buildHuffmanCodes(value, frequency, n);
		task.printTree(root, "");
	}
}

Output

 e 00
 f 010
 g 0110
 b 0111
 d 10
 a 110
 c 111
<?php
/*
    Php Program 
    Implement priority queue with pair
*/
class TreeNode
{
	public $first;
	public $second;
	public $left;
	public $right;

	function __construct($first, $second)
	{
		$this->first = $first;
		$this->second = $second;
		$this->left = null;
		$this->right = null;
	}
}
class QNode
{
	public $n;
	public $next;
	public $prev;

	function __construct($n)
	{
		$this->n = $n;
		$this->prev = null;
		$this->next = null;
	}
}
class PriorityQueue
{
	public $front;
	public $rear;
	public $size;

	function __construct()
	{
		$this->front = null;
		$this->rear = null;
		$this->size = 0;
	}
	// Add a node into queue Priority queue
	public	function enQueue($auxiliary)
	{
		//Create a dynamic node
		$node = new QNode($auxiliary);
		$node->n = $auxiliary;
		if ($this->front == null)
		{
			// When adding a first node of queue
			$this->front = $node;
			$this->rear = $node;
		}
		else if ($this->front->n->first >= $auxiliary->first)
		{
			// Add node at beginning position
			$node->next = $this->front;
			$this->front->prev = $node;
			$this->front = $node;
		}
		else if ($this->rear->n->first <= $auxiliary->first)
		{
			// Add node at last position
			$node->prev = $this->rear;
			$this->rear->next = $node;
			$this->rear = $node;
		}
		else
		{
			$temp = $this->front;
			// Find the location of inserting priority node
			while ($temp->n->first < $auxiliary->first)
			{
				$temp = $temp->next;
			}
			// Add node
			$node->next = $temp;
			$node->prev = $temp->prev;
			$temp->prev = $node;
			if ($node->prev != null)
			{
				$node->prev->next = $node;
			}
		}
		$this->size = $this->size + 1;
	}
	public	function isEmpty()
	{
		if ($this->size == 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	// Get a front element of queue
	public	function peek()
	{
		if ($this->isEmpty() == true)
		{
			// When Queue is empty
			echo "\n Empty Queue \n";
			return null;
		}
		else
		{
			return $this->front->n;
		}
	}
	public	function isSize()
	{
		return $this->size;
	}
	// Remove a front node of a queue
	public	function deQueue()
	{
		if ($this->isEmpty() == false)
		{
			$temp = $this->front;
			$temp->n = null;
			if ($this->front == $this->rear)
			{
				// When queue contains only one node
				$this->rear = null;
				$this->front = null;
			}
			else
			{
				$this->front = $this->front->next;
				$this->front->prev = null;
			}
			// Change queue size
			$this->size--;
		}
	}
	// Print elements of queue
	public	function printQdata()
	{
		$node = $this->front;
		echo "\n Queue Element ";
		while ($node != null)
		{
			echo "\n ". $node->n->first ." ". $node->n->second;
			$node = $node->next;
		}
		echo "\n";
	}
}
class HuffmanCodes
{
	// Display Huffman code
	public	function printTree($node, $result)
	{
		if ($node == null)
		{
			return;
		}
		if ($node->left == null && $node->right == null)
		{
			echo "\n ". $node->second ." ". $result;
			return;
		}
		$this->printTree($node->left, $result ."0");
		$this->printTree($node->right, $result ."1");
	}
	// Construct Huffman Code Tree
	public	function buildHuffmanCodes( & $value, & $frequency, $n)
	{
		$q = new PriorityQueue();
		$root = null;
		$n1 = null;
		$n2 = null;
		// First add all elements into priority queue
		for ($i = 0; $i < $n; ++$i)
		{
			$root = new TreeNode($frequency[$i], $value[$i]);
			$q->enQueue($root);
		}
		// q.printQdata();
		// Execute loop until the priority queue contains more than 1 node
		while ($q->isSize() > 1)
		{
			// Get first smallest node
			$n1 = $q->peek();
			//Remove a front element
			$q->deQueue();
			// Get second smallest node
			$n2 = $q->peek();
			// Remove a front element
			$q->deQueue();
			// Make new node using two smallest node
			$root = new TreeNode($n1->first + $n2->first, ' ');
			// Add new node into priority queue
			$q->enQueue($root);
			// Set left and right child
			$root->left = $n1;
			$root->right = $n2;
		}
		$q->deQueue();
		return $root;
	}
}

function main()
{
	$task = new HuffmanCodes();
	$value = array('a', 'b', 'c', 'd', 'e', 'f', 'g');
	$frequency = array(16, 8, 19, 32, 21, 10, 5);
	$n = count($frequency);
	$root = $task->buildHuffmanCodes($value, $frequency, $n);
	$task->printTree($root, "");
}
main();

Output

 e 00
 f 010
 g 0110
 b 0111
 d 10
 a 110
 c 111
/*
    Node Js Program 
    Implement priority queue with pair
*/
class TreeNode
{
	constructor(first, second)
	{
		this.first = first;
		this.second = second;
		this.left = null;
		this.right = null;
	}
}
class QNode
{
	constructor(n)
	{
		this.n = n;
		this.prev = null;
		this.next = null;
	}
}
class PriorityQueue
{
	constructor()
	{
		this.front = null;
		this.rear = null;
		this.size = 0;
	}
	// Add a node into queue Priority queue
	enQueue(auxiliary)
	{
		//Create a dynamic node
		var node = new QNode(auxiliary);
		node.n = auxiliary;
		if (this.front == null)
		{
			// When adding a first node of queue
			this.front = node;
			this.rear = node;
		}
		else if (this.front.n.first >= auxiliary.first)
		{
			// Add node at beginning position
			node.next = this.front;
			this.front.prev = node;
			this.front = node;
		}
		else if (this.rear.n.first <= auxiliary.first)
		{
			// Add node at last position
			node.prev = this.rear;
			this.rear.next = node;
			this.rear = node;
		}
		else
		{
			var temp = this.front;
			// Find the location of inserting priority node
			while (temp.n.first < auxiliary.first)
			{
				temp = temp.next;
			}
			// Add node
			node.next = temp;
			node.prev = temp.prev;
			temp.prev = node;
			if (node.prev != null)
			{
				node.prev.next = node;
			}
		}
		this.size = this.size + 1;
	}
	isEmpty()
	{
		if (this.size == 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	// Get a front element of queue
	peek()
	{
		if (this.isEmpty() == true)
		{
			// When Queue is empty
			process.stdout.write("\n Empty Queue \n");
			return null;
		}
		else
		{
			return this.front.n;
		}
	}
	isSize()
	{
		return this.size;
	}
	// Remove a front node of a queue
	deQueue()
	{
		if (this.isEmpty() == false)
		{
			var temp = this.front;
			temp.n = null;
			if (this.front == this.rear)
			{
				// When queue contains only one node
				this.rear = null;
				this.front = null;
			}
			else
			{
				this.front = this.front.next;
				this.front.prev = null;
			}
			// Change queue size
			this.size--;
		}
	}
	// Print elements of queue
	printQdata()
	{
		var node = this.front;
		process.stdout.write("\n Queue Element ");
		while (node != null)
		{
			process.stdout.write("\n " + node.n.first + " " + node.n.second);
			node = node.next;
		}
		process.stdout.write("\n");
	}
}
class HuffmanCodes
{
	// Display Huffman code
	printTree(node, result)
	{
		if (node == null)
		{
			return;
		}
		if (node.left == null && node.right == null)
		{
			process.stdout.write("\n " + node.second + " " + result);
			return;
		}
		this.printTree(node.left, result + "0");
		this.printTree(node.right, result + "1");
	}
	// Construct Huffman Code Tree
	buildHuffmanCodes(value, frequency, n)
	{
		var q = new PriorityQueue();
		var root = null;
		var n1 = null;
		var n2 = null;
		// First add all elements into priority queue
		for (var i = 0; i < n; ++i)
		{
			root = new TreeNode(frequency[i], value[i]);
			q.enQueue(root);
		}
		// q.printQdata();
		// Execute loop until the priority queue contains more than 1 node
		while (q.isSize() > 1)
		{
			// Get first smallest node
			n1 = q.peek();
			//Remove a front element
			q.deQueue();
			// Get second smallest node
			n2 = q.peek();
			// Remove a front element
			q.deQueue();
			// Make new node using two smallest node
			root = new TreeNode(n1.first + n2.first, ' ');
			// Add new node into priority queue
			q.enQueue(root);
			// Set left and right child
			root.left = n1;
			root.right = n2;
		}
		q.deQueue();
		return root;
	}
}

function main()
{
	var task = new HuffmanCodes();
	var value = ['a', 'b', 'c', 'd', 'e', 'f', 'g'];
	var frequency = [16, 8, 19, 32, 21, 10, 5];
	var n = frequency.length;
	var root = task.buildHuffmanCodes(value, frequency, n);
	task.printTree(root, "");
}
main();

Output

 e 00
 f 010
 g 0110
 b 0111
 d 10
 a 110
 c 111
#  Python 3 Program 
#  Implement priority queue with pair

class TreeNode :
	
	def __init__(self, first, second) :
		self.first = first
		self.second = second
		self.left = None
		self.right = None
	

class QNode :
	
	def __init__(self, n) :
		self.n = n
		self.prev = None
		self.next = None
	

class PriorityQueue :
	
	def __init__(self) :
		self.front = None
		self.rear = None
		self.size = 0
	
	#  Add a node into queue Priority queue
	def enQueue(self, auxiliary) :
		# Create a dynamic node
		node = QNode(auxiliary)
		node.n = auxiliary
		if (self.front == None) :
			#  When adding a first node of queue
			self.front = node
			self.rear = node
		
		elif(self.front.n.first >= auxiliary.first) :
			#  Add node at beginning position
			node.next = self.front
			self.front.prev = node
			self.front = node
		
		elif(self.rear.n.first <= auxiliary.first) :
			#  Add node at last position
			node.prev = self.rear
			self.rear.next = node
			self.rear = node
		else :
			temp = self.front
			#  Find the location of inserting priority node
			while (temp.n.first < auxiliary.first) :
				temp = temp.next
			
			#  Add node
			node.next = temp
			node.prev = temp.prev
			temp.prev = node
			if (node.prev != None) :
				node.prev.next = node
			
		
		self.size = self.size + 1
	
	def isEmpty(self) :
		if (self.size == 0) :
			return True
		else :
			return False
		
	
	#  Get a front element of queue
	def peek(self) :
		if (self.isEmpty() == True) :
			#  When Queue is empty
			print("\n Empty Queue ")
			return None
		else :
			return self.front.n
		
	
	def isSize(self) :
		return self.size
	
	#  Remove a front node of a queue
	def deQueue(self) :
		if (self.isEmpty() == False) :
			temp = self.front
			temp.n = None
			if (self.front == self.rear) :
				#  When queue contains only one node
				self.rear = None
				self.front = None
			else :
				self.front = self.front.next
				self.front.prev = None
			
			#  Change queue size
			self.size -= 1
		
	
	#  Print elements of queue
	def printQdata(self) :
		node = self.front
		print("\n Queue Element ", end = "")
		while (node != None) :
			print("\n ", node.n.first ," ", node.n.second, end = "")
			node = node.next
		
		print(end = "\n")
	

class HuffmanCodes :
	#  Display Huffman code
	def printTree(self, node, result) :
		if (node == None) :
			return
		
		if (node.left == None and node.right == None) :
			print("\n ", node.second ," ", result, end = "")
			return
		
		self.printTree(node.left, result+"0")
		self.printTree(node.right, result+"1")
	
	#  Construct Huffman Code Tree
	def buildHuffmanCodes(self, value, frequency, n) :
		q = PriorityQueue()
		root = None
		n1 = None
		n2 = None
		i = 0
		#  First add all elements into priority queue
		while (i < n) :
			root = TreeNode(frequency[i], value[i])
			q.enQueue(root)
			i += 1
		
		#  q.printQdata()
		#  Execute loop until the priority queue contains more than 1 node
		while (q.isSize() > 1) :
			#  Get first smallest node
			n1 = q.peek()
			# Remove a front element
			q.deQueue()
			#  Get second smallest node
			n2 = q.peek()
			#  Remove a front element
			q.deQueue()
			#  Make new node using two smallest node
			root = TreeNode(n1.first + n2.first, ' ')
			#  Add new node into priority queue
			q.enQueue(root)
			#  Set left and right child
			root.left = n1
			root.right = n2
		
		q.deQueue()
		return root
	

def main() :
	task = HuffmanCodes()
	value = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
	frequency = [16, 8, 19, 32, 21, 10, 5]
	n = len(frequency)
	root = task.buildHuffmanCodes(value, frequency, n)
	task.printTree(root, "")

if __name__ == "__main__": main()

Output

  e   00
  f   010
  g   0110
  b   0111
  d   10
  a   110
  c   111
#  Ruby Program 
#  Implement priority queue with pair

class TreeNode  
	# Define the accessor and reader of class TreeNode  
	attr_reader :first, :second, :left, :right
	attr_accessor :first, :second, :left, :right
 
	
	def initialize(first, second) 
		self.first = first
		self.second = second
		self.left = nil
		self.right = nil
	end

end

class QNode  
	# Define the accessor and reader of class QNode  
	attr_reader :n, :next, :prev
	attr_accessor :n, :next, :prev
 
	
	def initialize(n) 
		self.n = n
		self.prev = nil
		self.next = nil
	end

end

class PriorityQueue  
	# Define the accessor and reader of class PriorityQueue  
	attr_reader :front, :rear, :size
	attr_accessor :front, :rear, :size
 
	
	def initialize() 
		self.front = nil
		self.rear = nil
		self.size = 0
	end

	#  Add a node into queue Priority queue
	def enQueue(auxiliary) 
		# Create a dynamic node
		node = QNode.new(auxiliary)
		node.n = auxiliary
		if (self.front == nil) 
			#  When adding a first node of queue
			self.front = node
			self.rear = node
		elsif(self.front.n.first >= auxiliary.first) 
			#  Add node at beginning position
			node.next = self.front
			self.front.prev = node
			self.front = node
		elsif(self.rear.n.first <= auxiliary.first) 
			#  Add node at last position
			node.prev = self.rear
			self.rear.next = node
			self.rear = node
		else 
			temp = self.front
			#  Find the location of inserting priority node
			while (temp.n.first < auxiliary.first) 
				temp = temp.next
			end

			#  Add node
			node.next = temp
			node.prev = temp.prev
			temp.prev = node
			if (node.prev != nil) 
				node.prev.next = node
			end

		end

		self.size = self.size + 1
	end

	def isEmpty() 
		if (self.size == 0) 
			return true
		else 
			return false
		end

	end

	#  Get a front element of queue
	def peek() 
		if (self.isEmpty() == true) 
			#  When Queue is empty
			print("\n Empty Queue \n")
			return nil
		else 
			return self.front.n
		end

	end

	def isSize() 
		return self.size
	end

	#  Remove a front node of a queue
	def deQueue() 
		if (self.isEmpty() == false) 
			temp = self.front
			temp.n = nil
			if (self.front == self.rear) 
				#  When queue contains only one node
				self.rear = nil
				self.front = nil
			else 
				self.front = self.front.next
				self.front.prev = nil
			end

			#  Change queue size
			self.size -= 1
		end

	end

	#  Print elements of queue
	def printQdata() 
		node = self.front
		print("\n Queue Element ")
		while (node != nil) 
			print("\n ", node.n.first ," ", node.n.second)
			node = node.next
		end

		print("\n")
	end

end

class HuffmanCodes 
	#  Display Huffman code
	def printTree(node, result) 
		if (node == nil) 
			return
		end

		if (node.left == nil && node.right == nil) 
			print("\n ", node.second ," ", result)
			return
		end

		self.printTree(node.left, result+"0")
		self.printTree(node.right, result+"1")
	end

	#  Construct Huffman Code Tree
	def buildHuffmanCodes(value, frequency, n) 
		q = PriorityQueue.new()
		root = nil
		n1 = nil
		n2 = nil
		i = 0
		#  First add all elements into priority queue
		while (i < n) 
			root = TreeNode.new(frequency[i], value[i])
			q.enQueue(root)
			i += 1
		end

		#  q.printQdata()
		#  Execute loop until the priority queue contains more than 1 node
		while (q.isSize() > 1) 
			#  Get first smallest node
			n1 = q.peek()
			# Remove a front element
			q.deQueue()
			#  Get second smallest node
			n2 = q.peek()
			#  Remove a front element
			q.deQueue()
			#  Make new node using two smallest node
			root = TreeNode.new(n1.first + n2.first, ' ')
			#  Add new node into priority queue
			q.enQueue(root)
			#  Set left and right child
			root.left = n1
			root.right = n2
		end

		q.deQueue()
		return root
	end

end

def main() 
	task = HuffmanCodes.new()
	value = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
	frequency = [16, 8, 19, 32, 21, 10, 5]
	n = frequency.length
	root = task.buildHuffmanCodes(value, frequency, n)
	task.printTree(root, "")
end

main()

Output

 e 00
 f 010
 g 0110
 b 0111
 d 10
 a 110
 c 111
/*
    Scala Program 
    Implement priority queue with pair
*/
class TreeNode(var first: Int , var second: Character , var left: TreeNode , var right: TreeNode)
{
	def this(first: Int, second: Char)
	{
		this(first, second, null, null);
	}
}
class QNode(var n: TreeNode , var next: QNode , var prev: QNode)
{
	def this(n: TreeNode)
	{
		this(n, null, null);
	}
}
class PriorityQueue(var front: QNode , var rear: QNode , var size: Int)
{
	def this()
	{
		this(null, null, 0);
	}
	// Add a node into queue Priority queue
	def enQueue(auxiliary: TreeNode): Unit = {
		//Create a dynamic node
		var node: QNode = new QNode(auxiliary);
		node.n = auxiliary;
		if (this.front == null)
		{
			// When adding a first node of queue
			this.front = node;
			this.rear = node;
		}
		else if (this.front.n.first >= auxiliary.first)
		{
			// Add node at beginning position
			node.next = this.front;
			this.front.prev = node;
			this.front = node;
		}
		else if (this.rear.n.first <= auxiliary.first)
		{
			// Add node at last position
			node.prev = this.rear;
			this.rear.next = node;
			this.rear = node;
		}
		else
		{
			var temp: QNode = this.front;
			// Find the location of inserting priority node
			while (temp.n.first < auxiliary.first)
			{
				temp = temp.next;
			}
			// Add node
			node.next = temp;
			node.prev = temp.prev;
			temp.prev = node;
			if (node.prev != null)
			{
				node.prev.next = node;
			}
		}
		this.size = this.size + 1;
	}
	def isEmpty(): Boolean = {
		if (this.size == 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	// Get a front element of queue
	def peek(): TreeNode = {
		if (this.isEmpty() == true)
		{
			// When Queue is empty
			print("\n Empty Queue \n");
			return null;
		}
		else
		{
			return this.front.n;
		}
	}
	def isSize(): Int = {
		return this.size;
	}
	// Remove a front node of a queue
	def deQueue(): Unit = {
		if (this.isEmpty() == false)
		{
			var temp: QNode = this.front;
			temp.n = null;
			if (this.front == this.rear)
			{
				// When queue contains only one node
				this.rear = null;
				this.front = null;
			}
			else
			{
				this.front = this.front.next;
				this.front.prev = null;
			}
			// Change queue size
			this.size -= 1;
		}
	}
	// Print elements of queue
	def printQdata(): Unit = {
		var node: QNode = this.front;
		print("\n Queue Element ");
		while (node != null)
		{
			print("\n " + node.n.first + " " + node.n.second);
			node = node.next;
		}
		print("\n");
	}
}
class HuffmanCodes
{
	// Display Huffman code
	def printTree(node: TreeNode, result: String): Unit = {
		if (node == null)
		{
			return;
		}
		if (node.left == null && node.right == null)
		{
			print("\n " + node.second + " " + result);
			return;
		}
		this.printTree(node.left, result + "0");
		this.printTree(node.right, result + "1");
	}
	// Construct Huffman Code Tree
	def buildHuffmanCodes(value: Array[Character], frequency: Array[Int], n: Int): TreeNode = {
		var q: PriorityQueue = new PriorityQueue();
		var root: TreeNode = null;
		var n1: TreeNode = null;
		var n2: TreeNode = null;
		var i: Int = 0;
		// First add all elements into priority queue
		while (i < n)
		{
			root = new TreeNode(frequency(i), value(i));
			q.enQueue(root);
			i += 1;
		}
		// q.printQdata();
		// Execute loop until the priority queue contains more than 1 node
		while (q.isSize() > 1)
		{
			// Get first smallest node
			n1 = q.peek();
			//Remove a front element
			q.deQueue();
			// Get second smallest node
			n2 = q.peek();
			// Remove a front element
			q.deQueue();
			// Make new node using two smallest node
			root = new TreeNode(n1.first + n2.first, ' ');
			// Add new node into priority queue
			q.enQueue(root);
			// Set left and right child
			root.left = n1;
			root.right = n2;
		}
		q.deQueue();
		return root;
	}
}
object Main
{
	def main(args: Array[String]): Unit = {
		var task: HuffmanCodes = new HuffmanCodes();
		var value: Array[Character] = Array('a', 'b', 'c', 'd', 'e', 'f', 'g');
		var frequency: Array[Int] = Array(16, 8, 19, 32, 21, 10, 5);
		var n: Int = frequency.length;
		var root: TreeNode = task.buildHuffmanCodes(value, frequency, n);
		task.printTree(root, "");
	}
}

Output

 e 00
 f 010
 g 0110
 b 0111
 d 10
 a 110
 c 111
/*
    Swift 4 Program 
    Implement priority queue with pair
*/
class TreeNode
{
	var first: Int;
	var second: Character;
	var left: TreeNode? ;
	var right: TreeNode? ;
	init(_ first: Int, _ second: Character)
	{
		self.first = first;
		self.second = second;
		self.left = nil;
		self.right = nil;
	}
}
class QNode
{
	var n: TreeNode? ;
	var next: QNode? ;
	var prev: QNode? ;
	init(_ n: TreeNode? )
	{
		self.n = n;
		self.prev = nil;
		self.next = nil;
	}
}
class PriorityQueue
{
	var front: QNode? ;
	var rear: QNode? ;
	var size: Int;
	init()
	{
		self.front = nil;
		self.rear = nil;
		self.size = 0;
	}
	// Add a node into queue Priority queue
	func enQueue(_ auxiliary: TreeNode? )
	{
		//Create a dynamic node
		let node: QNode? = QNode(auxiliary);
		node!.n = auxiliary;
		if (self.front == nil)
		{
			// When adding a first node of queue
			self.front = node;
			self.rear = node;
		}
		else if (self.front!.n!.first >= auxiliary!.first)
		{
			// Add node at beginning position
			node!.next = self.front;
			self.front!.prev = node;
			self.front = node;
		}
		else if (self.rear!.n!.first <= auxiliary!.first)
		{
			// Add node at last position
			node!.prev = self.rear;
			self.rear!.next = node;
			self.rear = node;
		}
		else
		{
			var temp: QNode? = self.front;
			// Find the location of inserting priority node
			while (temp!.n!.first < auxiliary!.first)
			{
				temp = temp!.next;
			}
			// Add node
			node!.next = temp;
			node!.prev = temp!.prev;
			temp!.prev = node;
			if (node!.prev  != nil)
			{
				node!.prev!.next = node;
			}
		}
		self.size = self.size + 1;
	}
	func isEmpty()->Bool
	{
		if (self.size == 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	// Get a front element of queue
	func peek()->TreeNode?
	{
		if (self.isEmpty() == true)
		{
			// When Queue is empty
			print("\n Empty Queue ");
			return nil;
		}
		else
		{
			return self.front!.n;
		}
	}
	func isSize()->Int
	{
		return self.size;
	}
	// Remove a front node of a queue
	func deQueue()
	{
		if (self.isEmpty() == false)
		{
			let temp: QNode? = self.front;
			temp!.n = nil;
			if (self.front === self.rear)
			{
				// When queue contains only one node
				self.rear = nil;
				self.front = nil;
			}
			else
			{
				self.front = self.front!.next;
				self.front!.prev = nil;
			}
			// Change queue size
			self.size -= 1;
		}
	}
	// Print elements of queue
	func printQdata()
	{
		var node: QNode? = self.front;
		print("\n Queue Element ", terminator: "");
		while (node  != nil)
		{
			print("\n ", node!.n!.first ," ", node!.n!.second, terminator: "");
			node = node!.next;
		}
		print(terminator: "\n");
	}
}
class HuffmanCodes
{
	// Display Huffman code
	func printTree(_ node: TreeNode? , _ result : String)
	{
		if (node == nil)
		{
			return;
		}
		if (node!.left == nil && node!.right == nil)
		{
			print("\n ", node!.second ," ", result, terminator: "");
			return;
		}
		self.printTree(node!.left, result+"0");
		self.printTree(node!.right, result+"1");
	}
	// Construct Huffman Code Tree
	func buildHuffmanCodes(_ value: [Character], _ frequency: [Int], _ n: Int)->TreeNode?
	{
		let q: PriorityQueue = PriorityQueue();
		var root: TreeNode? = nil;
		var n1: TreeNode? = nil;
		var n2: TreeNode? = nil;
		var i: Int = 0;
		// First add all elements into priority queue
		while (i < n)
		{
			root = TreeNode(frequency[i], value[i]);
			q.enQueue(root);
			i += 1;
		}
		// q.printQdata();
		// Execute loop until the priority queue contains more than 1 node
		while (q.isSize() > 1)
		{
			// Get first smallest node
			n1 = q.peek();
			//Remove a front element
			q.deQueue();
			// Get second smallest node
			n2 = q.peek();
			// Remove a front element
			q.deQueue();
			// Make new node using two smallest node
			root = TreeNode(n1!.first + n2!.first, " ");
			// Add new node into priority queue
			q.enQueue(root);
			// Set left and right child
			root!.left = n1;
			root!.right = n2;
		}
		q.deQueue();
		return root;
	}
}
func main()
{
	let task: HuffmanCodes = HuffmanCodes();
	let value: [Character] = ["a", "b", "c", "d", "e", "f", "g"];
	let frequency: [Int] = [16, 8, 19, 32, 21, 10, 5];
	let n: Int = frequency.count;
	let root: TreeNode? = task.buildHuffmanCodes(value, frequency, n);
	task.printTree(root, "");
}
main();

Output

  e   00
  f   010
  g   0110
  b   0111
  d   10
  a   110
  c   111
/*
    Kotlin Program 
    Implement priority queue with pair
*/
class TreeNode
{
	var first: Int;
	var second: Char;
	var left: TreeNode ? ;
	var right: TreeNode ? ;
	constructor(first: Int, second: Char)
	{
		this.first = first;
		this.second = second;
		this.left = null;
		this.right = null;
	}
}
class QNode
{
	var n: TreeNode ? ;
	var next: QNode ? ;
	var prev: QNode ? ;
	constructor(n: TreeNode ? )
	{
		this.n = n;
		this.prev = null;
		this.next = null;
	}
}
class PriorityQueue
{
	var front: QNode ? ;
	var rear: QNode ? ;
	var size: Int;
	constructor()
	{
		this.front = null;
		this.rear = null;
		this.size = 0;
	}
	// Add a node into queue Priority queue
	fun enQueue(auxiliary: TreeNode ): Unit
	{
		//Create a dynamic node
		var node: QNode = QNode(auxiliary);
		node.n = auxiliary;
		if (this.front == null)
		{
			// When adding a first node of queue
			this.front = node;
			this.rear = node;
		}
		else if (this.front?.n!!.first >= auxiliary.first)
		{
			// Add node at beginning position
			node.next = this.front;
			this.front?.prev = node;
			this.front = node;
		}
		else if (this.rear?.n!!.first <= auxiliary.first)
		{
			// Add node at last position
			node.prev = this.rear;
			this.rear?.next = node;
			this.rear = node;
		}
		else
		{
			var temp: QNode ? = this.front;
			// Find the location of inserting priority node
			while (temp?.n!!.first < auxiliary.first)
			{
				temp = temp.next;
			}
			// Add node
			node.next = temp;
			node.prev = temp.prev;
			temp.prev = node;
			if (node.prev != null)
			{
				node.prev?.next = node;
			}
		}
		this.size = this.size + 1;
	}
	fun isEmpty(): Boolean
	{
		if (this.size == 0)
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	// Get a front element of queue
	fun peek(): TreeNode ?
	{
		if (this.isEmpty() == true)
		{
			// When Queue is empty
			print("\n Empty Queue \n");
			return null;
		}
		else
		{
			return this.front?.n;
		}
	}
	fun isSize(): Int
	{
		return this.size;
	}
	// Remove a front node of a queue
	fun deQueue(): Unit
	{
		if (this.isEmpty() == false)
		{
			var temp: QNode ? = this.front;
			temp?.n = null;
			if (this.front == this.rear)
			{
				// When queue contains only one node
				this.rear = null;
				this.front = null;
			}
			else
			{
				this.front = this.front?.next;
				this.front?.prev = null;
			}
			// Change queue size
			this.size -= 1;
		}
	}
	// Print elements of queue
	fun printQdata(): Unit
	{
		var node: QNode ? = this.front;
		print("\n Queue Element ");
		while (node != null)
		{
			print("\n " + node.n?.first + " " + node.n?.second);
			node = node.next;
		}
		print("\n");
	}
}
class HuffmanCodes
{
	// Display Huffman code
	fun printTree(node: TreeNode ? , result : String): Unit
	{
		if (node == null)
		{
			return;
		}
		if (node.left == null && node.right == null)
		{
			print("\n " + node.second + " " + result);
			return;
		}
		this.printTree(node.left, result + "0");
		this.printTree(node.right, result + "1");
	}
	// Construct Huffman Code Tree
	fun buildHuffmanCodes(value: Array <Char> , frequency: Array < Int > , n: Int): TreeNode ?
	{
		var q: PriorityQueue = PriorityQueue();
		var root: TreeNode ? = null;
		var n1: TreeNode ? ;
		var n2: TreeNode ? ;
		var i: Int = 0;
		// First add all elements into priority queue
		while (i < n)
		{
			root = TreeNode(frequency[i], value[i]);
			q.enQueue(root);
			i += 1;
		}
		// q.printQdata();
		// Execute loop until the priority queue contains more than 1 node
		while (q.isSize() > 1)
		{
			// Get first smallest node
			n1 = q.peek();
			//Remove a front element
			q.deQueue();
			// Get second smallest node
			n2 = q.peek();
			// Remove a front element
			q.deQueue();
			// Make new node using two smallest node
			root = TreeNode(n1!!.first + n2!!.first, ' ');
			// Add new node into priority queue
			q.enQueue(root);
			// Set left and right child
			root.left = n1;
			root.right = n2;
		}
		q.deQueue();
		return root;
	}
}
fun main(args: Array < String > ): Unit
{
	var task: HuffmanCodes = HuffmanCodes();
	var value: Array < Char > = arrayOf('a', 'b', 'c', 'd', 'e', 'f', 'g');
	var frequency: Array < Int > = arrayOf(16, 8, 19, 32, 21, 10, 5);
	var n: Int = frequency.count();
	var root: TreeNode ? = task.buildHuffmanCodes(value, frequency, n);
	task.printTree(root, "");
}

Output

 e 00
 f 010
 g 0110
 b 0111
 d 10
 a 110
 c 111



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