Added Huffman Encoding algorithm in Java

Java/Greedy_Algorithms/HuffmanEncoding.java

@@ -0,0 +1,79 @@
+import java.util.PriorityQueue;
+
+// Given a set of characters and their corresponding frequencies,
+// construct the Huffman Tree and generate Huffman Codes for each character.
+// The goal is to use fewer bits for more frequent characters to achieve lossless data compression.
+
+// Approach: Use a Greedy Algorithm by always combining the two nodes with the lowest frequencies.
+
+class HuffmanEncoding {
+
+    // Node class representing each character and its frequency
+    static class Node {
+        char ch;
+        int freq;
+        Node left, right;
+
+        Node(char ch, int freq) {
+            this.ch = ch;
+            this.freq = freq;
+        }
+
+        Node(int freq, Node left, Node right) {
+            this.ch = '-';
+            this.freq = freq;
+            this.left = left;
+            this.right = right;
+        }
+    }
+
+    // Comparator for the min-heap (PriorityQueue)
+    static class NodeComparator implements java.util.Comparator<Node> {
+        public int compare(Node a, Node b) {
+            return a.freq - b.freq;
+        }
+    }
+
+    // Recursive function to print Huffman codes from the root of the tree
+    static void printHuffmanCodes(Node root, String code) {
+        if (root == null) return;
+
+        // Leaf node: contains a character
+        if (root.left == null && root.right == null && root.ch != '-') {
+            System.out.println(root.ch + ": " + code);
+        }
+
+        printHuffmanCodes(root.left, code + "0");
+        printHuffmanCodes(root.right, code + "1");
+    }
+
+    public static void main(String[] args) {
+        // Example input: characters and their frequencies
+        char[] chars = { 'a', 'b', 'c', 'd', 'e', 'f' };
+        int[] freqs = { 5, 9, 12, 13, 16, 45 };
+
+        // Min-heap to store nodes
+        PriorityQueue<Node> pq = new PriorityQueue<>(new NodeComparator());
+
+        // Step 1: Create a leaf node for each character and add it to the queue
+        for (int i = 0; i < chars.length; i++) {
+            pq.add(new Node(chars[i], freqs[i]));
+        }
+
+        // Step 2: Combine the two lowest frequency nodes until one remains
+        while (pq.size() > 1) {
+            Node left = pq.poll();
+            Node right = pq.poll();
+
+            Node merged = new Node(left.freq + right.freq, left, right);
+            pq.add(merged);
+        }
+
+        // Root of the Huffman Tree
+        Node root = pq.poll();
+
+        // Step 3: Print Huffman codes
+        System.out.println("Huffman Codes:");
+        printHuffmanCodes(root, "");
+    }
+}