diff --git a/Others/Huffman.java b/Others/Huffman.java new file mode 100644 index 000000000..43366046b --- /dev/null +++ b/Others/Huffman.java @@ -0,0 +1,135 @@ +import java.util.PriorityQueue; +import java.util.Scanner; +import java.util.Comparator; + +// node class is the basic structure +// of each node present in the Huffman - tree. +class HuffmanNode { + + int data; + char c; + + HuffmanNode left; + HuffmanNode right; +} + +// comparator class helps to compare the node +// on the basis of one of its attribute. +// Here we will be compared +// on the basis of data values of the nodes. +class MyComparator implements Comparator { + public int compare(HuffmanNode x, HuffmanNode y) + { + + return x.data - y.data; + } +} + +public class Huffman { + + // recursive function to print the + // huffman-code through the tree traversal. + // Here s is the huffman - code generated. + public static void printCode(HuffmanNode root, String 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 + && Character.isLetter(root.c)) { + + // c is the character in the node + System.out.println(root.c + ":" + s); + + 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 + public static void main(String[] args) + { + + Scanner s = new Scanner(System.in); + + // number of characters. + int n = 6; + char[] charArray = { 'a', 'b', 'c', 'd', 'e', 'f' }; + int[] charfreq = { 5, 9, 12, 13, 16, 45 }; + + // creating a priority queue q. + // makes a min-priority queue(min-heap). + PriorityQueue q + = new PriorityQueue(n, new MyComparator()); + + for (int i = 0; i < n; i++) { + + // creating a Huffman node object + // and add it to the priority queue. + HuffmanNode 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.add(hn); + } + + // create a root node + HuffmanNode root = null; + + // 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.size() > 1) { + + // first min extract. + HuffmanNode x = q.peek(); + q.poll(); + + // second min extarct. + HuffmanNode y = q.peek(); + q.poll(); + + // new node f which is equal + HuffmanNode 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.add(f); + } + + // print the codes by traversing the tree + printCode(root, ""); + } +} +