Added Huffman Code Algo (greedy,priority queue,recursion)

Author: pulkit4tech

Huffman_Coding.java

@@ -0,0 +1,100 @@
+
+/**
+*
+* @author pulkit4tech
+*/
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.util.Comparator;
+import java.util.PriorityQueue;
+
+// Huffman Coding for lossless data compression
+// Greedy Algorithm
+class Huffman_Coding implements Runnable {
+
+	BufferedReader c;
+	PrintWriter pout;
+	// static long mod = 1000000007;
+
+	public void run() {
+		try {
+			c = new BufferedReader(new InputStreamReader(System.in));
+			pout = new PrintWriter(System.out, true);
+			solve();
+			pout.close();
+		} catch (Exception e) {
+			pout.close();
+			e.printStackTrace();
+			System.exit(1);
+		}
+	}
+
+	public static void main(String[] args) throws Exception {
+		new Thread(new Huffman_Coding()).start();
+	}
+
+	void solve() throws Exception {
+		Huffman();
+	}
+
+	void Huffman() {
+		char arr[] = { 'p', 'u', 'l', 'k', 'i', 't' };
+		long freq[] = { 1, 1, 12, 13, 16, 45 };
+		int size = arr.length;
+		HuffmanCodes(arr, freq, size);
+	}
+
+	class MinHeapNode {
+		char data;
+		long freq;
+		MinHeapNode left, right;
+
+		public MinHeapNode(char data, long freq) {
+			this.data = data;
+			this.freq = freq;
+		}
+	}
+
+	void HuffmanCodes(char data[], long freq[], int size) {
+		MinHeapNode left, right, top;
+
+		PriorityQueue<MinHeapNode> pq = new PriorityQueue<>(new Comparator<MinHeapNode>() {
+
+			@Override
+			public int compare(MinHeapNode o1, MinHeapNode o2) {
+				// TODO Auto-generated method stub
+				return Long.compare(o1.freq, o2.freq);
+			}
+		});
+
+		for (int i = 0; i < size; i++) {
+			pq.add(new MinHeapNode(data[i], freq[i]));
+		}
+
+		while (pq.size() != 1) {
+			left = pq.poll();
+			right = pq.poll();
+
+			top = new MinHeapNode('$', left.freq + right.freq);
+			top.left = left;
+			top.right = right;
+
+			pq.add(top);
+		}
+
+		printCodes(pq.peek(), "");
+	}
+
+	void printCodes(MinHeapNode root, String str) {
+		if (root == null)
+			return;
+
+		if (root.data != '$')
+			pout.println(root.data + ":" + str);
+
+		printCodes(root.left, str + "0");
+		printCodes(root.right, str + "1");
+	}
+
+}