Added Vedang's huffman coding code.

2025-10-12 15:13:52 +05:30
parent 16b452316e
commit 77bf4d569d
1 changed files with 135 additions and 0 deletions
@@ -0,0 +1,135 @@
+import java.util.*;
+
+public class Code_A2 {
+    private static HuffmanNode root;
+    private static Map<Character, String> huffmanCodes = new HashMap<>();
+    private static Map<Character, Integer> freqMap = new HashMap<>();
+    private static String inputText = "";
+
+    static class HuffmanNode implements Comparable<HuffmanNode> {
+        char ch;
+        int freq;
+        HuffmanNode left, right;
+
+        HuffmanNode(char ch, int freq) {
+            this.ch = ch;
+            this.freq = freq;
+        }
+
+        public int compareTo(HuffmanNode other) {
+            return this.freq - other.freq;
+        }
+    }
+
+    private static void generateCodes(HuffmanNode node, String code) {
+        if (node == null) return;
+        if (node.left == null && node.right == null)
+            huffmanCodes.put(node.ch, code);
+        generateCodes(node.left, code + "0");
+        generateCodes(node.right, code + "1");
+    }
+
+    private static void buildHuffmanTree() {
+        PriorityQueue<HuffmanNode> pq = new PriorityQueue<>();
+        for (Map.Entry<Character, Integer> e : freqMap.entrySet())
+            pq.add(new HuffmanNode(e.getKey(), e.getValue()));
+
+        while (pq.size() > 1) {
+            HuffmanNode left = pq.poll();
+            HuffmanNode right = pq.poll();
+            HuffmanNode parent = new HuffmanNode('-', left.freq + right.freq);
+            parent.left = left; parent.right = right;
+            pq.add(parent);
+        }
+        root = pq.peek();
+        huffmanCodes.clear();
+        generateCodes(root, "");
+    }
+
+    private static void displayCodes() {
+        if (huffmanCodes.isEmpty()) {
+            System.out.println("No Huffman codes generated yet!");
+            return;
+        }
+        System.out.println("\nCharacter\tFrequency\tHuffman Code");
+        for (Map.Entry<Character, String> entry : huffmanCodes.entrySet())
+            System.out.println(entry.getKey() + "\t\t" + freqMap.get(entry.getKey()) + "\t\t" + entry.getValue());
+    }
+
+    private static void encodeText() {
+        if (huffmanCodes.isEmpty()) {
+            System.out.println("Please build Huffman Tree first!");
+            return;
+        }
+        StringBuilder encoded = new StringBuilder();
+        for (char c : inputText.toCharArray())
+            encoded.append(huffmanCodes.get(c));
+        System.out.println("\nEncoded Text: " + encoded.toString());
+    }
+
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        while (true) {
+            System.out.println("\n=== Huffman Encoding Menu ===");
+            System.out.println("1. Enter input string (auto frequency)");
+            System.out.println("2. Enter characters with frequencies manually");
+            System.out.println("3. Build Huffman Tree & display codes");
+            System.out.println("4. Encode the text");
+            System.out.println("5. Exit");
+            System.out.print("Enter your choice: ");
+            int choice = sc.nextInt();
+            sc.nextLine();
+
+            switch (choice) {
+                case 1:
+                    System.out.print("Enter the text: ");
+                    inputText = sc.nextLine();
+                    freqMap.clear();
+                    for (char c : inputText.toCharArray())
+                        freqMap.put(c, freqMap.getOrDefault(c, 0) + 1);
+                    break;
+
+                case 2:
+                    freqMap.clear();
+                    inputText = "";
+                    System.out.print("Enter number of characters: ");
+                    int n = sc.nextInt();
+                    sc.nextLine();
+                    for (int i = 0; i < n; i++) {
+                        System.out.print("Character " + (i + 1) + ": ");
+                        char c = sc.nextLine().charAt(0);
+                        System.out.print("Frequency of " + c + ": ");
+                        int f = sc.nextInt();
+                        sc.nextLine();
+                        freqMap.put(c, f);
+                        inputText += String.valueOf(c).repeat(f);
+                    }
+                    break;
+
+                case 3:
+                    if (freqMap.isEmpty()) {
+                        System.out.println("Please enter input first!");
+                    } else {
+                        buildHuffmanTree();
+                        displayCodes();
+                    }
+                    break;
+
+                case 4:
+                    if (inputText.isEmpty())
+                        System.out.println("Enter input text first!");
+                    else
+                        encodeText();
+                    break;
+
+                case 5:
+                    System.out.println("Exiting program. Goodbye!");
+                    sc.close();
+                    return;
+
+                default:
+                    System.out.println("Invalid choice!");
+            }
+        }
+    }
+}