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Thread: Dictionary using Distributed Hash Table and BST Tree

  1. #26
    Super Moderator Norm's Avatar
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    Default Re: Dictionary using Distributed Hash Table and BST Tree

    How/where did you get the algorithm for the code in the hash() method?

    What are the meanings for the constants: 53 and 96?

    It should give me numbers 1-7 and for "g" it gives me 0.
    Execute the method with single letters from a to z and see what is returned. The pattern should give you some idea how to fix it.
    Last edited by Norm; June 23rd, 2012 at 11:24 AM.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Dictionary using Distributed Hash Table and BST Tree

    So: 1. I got it from a friend.
    2. constant 53 is: number of small letters + big letters + space.
    3. 96 is the code of "`" before "a" in the ASCII code.
    4. l is the size of the dictionary.

    I noticed it is only good for the lower case letters.
    corrected:
    public static int hash(String key, int l)
        {
            int value = 0;
     
            for(int j = 0; j < key.length(); j++ ) 
            {
                value = (value * 53 + toDig(key.charAt(j))); 
            }
     
            value = value % l;
     
            return value;
        }
     
        private static int toDig(char a)
        {
            int hMany = 0;
            if(Character.isLowerCase(a))
            {
                hMany = a - ('a' - 1);
            } else if(Character.isUpperCase(a)) {
                hMany = a - ('A' - 27);
            } else if(a == ' '){
                hMany = 53;
            }
            return hMany;
        }

    //It works now.
    Last edited by dezett; June 23rd, 2012 at 12:02 PM.

  3. #28
    Super Moderator Norm's Avatar
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    Default Re: Dictionary using Distributed Hash Table and BST Tree

    When posting code please wrap your code with
    [code=java]
    <YOUR CODE HERE>
    [/code]
    to get highlighting and preserve formatting.
    If you don't understand my answer, don't ignore it, ask a question.

  4. #29
    Super Moderator Norm's Avatar
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    Default Re: Dictionary using Distributed Hash Table and BST Tree

    There is a substring() method call on line 39 where the value of the index is out of bounds/past the end of the String.
    Look at the code on that line and see why: how long is the String & what is the value of the index.
    Use a println to print out those values if you need to see what they are.

    One problem with the code is the last else does NOT test the first letter of the function String. It should test for that and there should be an ending else clause that prints an error message if none of the above test were true.
    Last edited by Norm; June 23rd, 2012 at 12:08 PM. Reason: missing test and else
    If you don't understand my answer, don't ignore it, ask a question.

  5. The Following User Says Thank You to Norm For This Useful Post:

    dezett (October 18th, 2012)

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