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Thread: Regex or String Algoritham

  1. #1
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    Default Regex or String Algoritham

    Hello please,
    Appreciate your help here.
    I have a field string that wants to find if that exists between two range strings on character basis.


    String lower boundary : "ABD"
    String upper boundary : "ALGKP"
    field String : "ABE"

    Now the field string "ABE" exists between "ABD" and "ALGKP".
    Here the comparison is char-by-char. i.e
    A is b/w A & A, true
    B is b/w B and L, true
    E is b/w D and G, true
    So finally returns true.

    Another example:

    For the same above boundaries, if the field string is "ABC", it should return false since C not b/w D & P.
    For the same above boundaries, if the field string is "AB", it should return true.


  2. #2
    mmm.. coffee JavaPF's Avatar
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    Default Re: Regex or String Algoritham

    Hello and welcome to the forums.

    What are you stuck on? Have you attempted any code?

    On the subject of RegEx, please read - http://www.javaprogrammingforums.com...explained.html
    Please use [highlight=Java] code [/highlight] tags when posting your code.
    Forum Tip: Add to peoples reputation by clicking the button on their useful posts.

  3. #3
    Super Moderator helloworld922's Avatar
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    Default Re: Regex or String Algoritham

    Are trying to write your own "regex" engine? If you are, I would recommend reading on finite state automata/finite state machines. While the deterministic state machines are really the only ones that can actually be handled by a computer, you may want to also read about non-deterministic state machines as well as these are much easier for people to design and can be converted into a deterministic state machine with some clever thinking.

  4. #4
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    Default Re: Regex or String Algoritham

    One of the tricks I like to use with these kind of String computation problems is to treat the characters in the string like numbers. Try using charAt then casting the char into an int. The value of the int will be in the range 65..90 for 'A' to 'Z' (case sensitive). This will reduce your problem to a simple integer range check.

  5. #5
    Grand Poobah
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    Default Re: Regex or String Algoritham

    1. Why revive a thread that is several months old?

    2. Why not just make 2 calls to compareTo? Even if you had to write the code yourself, why fanny about converting chars to ints?
    System.out.println('a' < 'b');
    Improving the world one idiot at a time!

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