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Thread: Huffman coding from huffman tree...

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    Default Huffman coding from huffman tree...

    hi there, need some help with my huffman coding assignment...
    actually, i had done tree huffman tree part... now left the part which stresses me for days... can't really come out with a working code for generating the huffman code.
    all i need is to extract the code, which is (for example 01010101) to represent the last character at the leaf of the huffman tree...
    the way i define the nodes are as follows...
    [code : java]
    class Node
    {
    public String item;
    public Node leftChild;
    public Node rightChild;
    public Node getLeft(){return leftChild;}
    public Node getRight(){return rightChild;}
    public String getKey(){return item;}
    }
    i have a working tree which i check by listing the traversal of it, and now, can anyone help me out with generating the huffman bit code for the huffman tree? the huffman tree starts with the root, have the value of the frequency in the internode and the leaf are representing the character of the text file i was to encode.
    any suggestion or ideas are deeply appreciated.
    regards, tetkun.


  2. #2
    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: Huffman coding from huffman tree...

    Before you sit down to code, you have to think about exactly what you need to do. Pretend you have a really dumb friend who knows nothing about Huffman trees. Write instructions that the friend could follow to get the job done. Remember, he doesn't know anything, so the instructions have to be as exact as possible.

    When you have those written out (not in code, just plain language), then you'll have an algorithm that you can worry about writing code for.
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    Default Re: Huffman coding from huffman tree...

    hi kevin,
    thanks for the reply.
    i understand what you mean... actually, i'm more to a vb user, but learning java now for my master assignments... i previously work as a math teacher for 7 years and continues master in IT because of knowledge and programming experience i have in IT and on top of it, i'm interested to learn the language of many not fond of in my country. therefore with the lack of fundamental and experience in using java, internet have always been the source of searching understandable code as a reference. for the problem above, i didn't copy the whole code from other since my lecture say that's it's ok, but i try my own after understanding my first assignment on constructing a binary tree which i use the coding from CHINMAY LOKESH (acknowledgment was given). based on understanding towards the huffman coding... this is what i did for my 2nd assignment.
    1. read the text file
    2. rearrange the characters using quicksort
    3. count the frequency from the first till the end
    4. sort the frequency with corresponding character using bubble sort (just to utilize what i learn from lectures)
    5. create the huffman tree (using recursion with binary tree experience)
    6. generate the coding from the tree... (the last part of the assignment)

    i don't know why, it took me a whole day of thinking but i cannot solve it using recursion. alas.. when i woke up this morning, something new came up... i don't know how it happened but it was a logic solution apart from recursion. i manage to solve it. this is the code. do comment a bit about it and i would sure like to know other method of doing so. i will try to understand the coding.
     
    public void PrintCode()
        {
            Queue<Node> level  = new LinkedList<>();
            Queue<String> code = new LinkedList<>();
     
            level.add(root);
            code.add(" ");
            while(!level.isEmpty()){
                Node node = level.poll();
                String str = code.poll();
     
                if(node.leftChild != null)
                {
                	level.add(node.leftChild);
                	code.add(str + "1");
                }
     
                if(node.rightChild != null)
                {
                	level.add(node.rightChild);
                	code.add(str + "0");
                }
                else
                {
                	System.out.println(node.item + " -" + str);
                }
            }
     
        }
    any response or amendment are most welcome. thanks. nice day.
    Last edited by pbrockway2; April 23rd, 2013 at 07:31 PM. Reason: code tags edited

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