arrays

Discussion in 'Java' started by iVan on CSC 101, Feb 16, 2007.

  1. hi to all!....I'm really having having problms with this array
    thing...our instructor just gave us 15 pages copy all about Arrays and
    of course problms about it...I have 5 problems and really don't know
    how to solve these.....geezzz.....they suck!...=D...hhmmmm...anyway
    i'm here for any help from you guys...

    beginners like us really need ( I think) to have lectures by those who
    should do it but I dunnot know why they're just giving us this stuff
    without explanations...hhhhmmm....

    nyways, here are the problems about Arrays....

    1. Longest plateau. Given an array of integers, find the length and
    location of the longest contiguous sequence of
    equal values.

    2. Bad shuffling. Suppose that you choose a random integer between 0
    and N-1 in Shuffle.java instead of 0 and i.
    Show that the resulting order is not equally likely to be one ot
    the N! possibilities, even whenn N-3. Assuming
    the elements are named A, B, and C, verify that all 6 outcomes are
    possible, but that theu occur with the
    following baised probabilities.

    ABC ACB BAC BCA CAB CBA
    4/27 5/27 6/27 4/27
    5/27 3/27

    3. Scheduling with deadline. Suppose that you have N tasks to
    schedule. Each task takes 1 unit of time and has
    a deadling by which time it is expected to finish. If a task is
    not completed by its deadline, you pay a $1,000
    fine. Find a schedule that minimizes the penalty. Hint: schedule
    the tasks in order of their deadline, but don't
    bother with any task that won't finish by its deadline.

    4. Magic squares. Write a program MagicSquare.java that reads in an
    odd integer N form the command line and prints our an N-by-N magic
    square. the square contains each of the integers between 1 and N^2
    exactly once, such that all row sums, column sums, and diagonal sums
    are equal.

    4 9 2 11 18 25 2 9
    3 5 7 10 12 19 21 3
    8 1 6 4 6 13 20 22
    12 5 7 14 16
    17 24 1 8 15


    lastly,
    5. US postal barcodes. The POSTNET barcode is used by the US Postal
    System to route mail. Each decimal digit in the zip code is encoded
    using a sequence of 5 short lines for use by scanners as follows:

    Value Encoding
    0 I I i i i
    1 i i i I I
    2 i i I i I
    3 i i I I i
    4 i I i i I
    5 i I i I i
    6 i I I i i
    7 I i i i I
    8 I i i I i
    9 I i I i i

    i = are small bar lines
    I = are the larger ones

    thank you so much for reading dude!.....hoping for your positive
    response.....badly needing it for our midterms....

    you could also email me at ....thanks a
    lot!...... ^ ^

    God bless dudes!!!!
     
    iVan on CSC 101, Feb 16, 2007
    #1
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  2. iVan on CSC 101

    Daniel Pitts Guest

    On Feb 15, 4:52 pm, "iVan on CSC 101" <>
    wrote:
    > hi to all!....I'm really having having problms with this array
    > thing...our instructor just gave us 15 pages copy all about Arrays and
    > of course problms about it...I have 5 problems and really don't know
    > how to solve these.....geezzz.....they suck!...=D...hhmmmm...anyway
    > i'm here for any help from you guys...
    >
    > beginners like us really need ( I think) to have lectures by those who
    > should do it but I dunnot know why they're just giving us this stuff
    > without explanations...hhhhmmm....
    >
    > nyways, here are the problems about Arrays....
    >
    > 1. Longest plateau. Given an array of integers, find the length and
    > location of the longest contiguous sequence of
    > equal values.
    >
    > 2. Bad shuffling. Suppose that you choose a random integer between 0
    > and N-1 in Shuffle.java instead of 0 and i.
    > Show that the resulting order is not equally likely to be one ot
    > the N! possibilities, even whenn N-3. Assuming
    > the elements are named A, B, and C, verify that all 6 outcomes are
    > possible, but that theu occur with the
    > following baised probabilities.
    >
    > ABC ACB BAC BCA CAB CBA
    > 4/27 5/27 6/27 4/27
    > 5/27 3/27
    >
    > 3. Scheduling with deadline. Suppose that you have N tasks to
    > schedule. Each task takes 1 unit of time and has
    > a deadling by which time it is expected to finish. If a task is
    > not completed by its deadline, you pay a $1,000
    > fine. Find a schedule that minimizes the penalty. Hint: schedule
    > the tasks in order of their deadline, but don't
    > bother with any task that won't finish by its deadline.
    >
    > 4. Magic squares. Write a program MagicSquare.java that reads in an
    > odd integer N form the command line and prints our an N-by-N magic
    > square. the square contains each of the integers between 1 and N^2
    > exactly once, such that all row sums, column sums, and diagonal sums
    > are equal.
    >
    > 4 9 2 11 18 25 2 9
    > 3 5 7 10 12 19 21 3
    > 8 1 6 4 6 13 20 22
    > 12 5 7 14 16
    > 17 24 1 8 15
    >
    > lastly,
    > 5. US postal barcodes. The POSTNET barcode is used by the US Postal
    > System to route mail. Each decimal digit in the zip code is encoded
    > using a sequence of 5 short lines for use by scanners as follows:
    >
    > Value Encoding
    > 0 I I i i i
    > 1 i i i I I
    > 2 i i I i I
    > 3 i i I I i
    > 4 i I i i I
    > 5 i I i I i
    > 6 i I I i i
    > 7 I i i i I
    > 8 I i i I i
    > 9 I i I i i
    >
    > i = are small bar lines
    > I = are the larger ones
    >
    > thank you so much for reading dude!.....hoping for your positive
    > response.....badly needing it for our midterms....
    >
    > you could also email me at ....thanks a
    > lot!...... ^ ^
    >
    > God bless dudes!!!!


    Some advice:
    Consider how much time you spent copying the description of your
    homework assignment. Then consider how much you learned by copying it
    over.
    Next, consider how much time you would have saved by at least trying
    some of the assignment yourself before posting. Also, consider how
    much more you would have learned by trying.

    After you consider that, make at least an ATTEMPT at it, tell us whats
    gone wrong, and someone may feel inclined to help you understand.

    If you want someone to DO your homework, rather than help you
    understand it, feel free to pay someone, but don't bother applying for
    a job as a programmer.
     
    Daniel Pitts, Feb 16, 2007
    #2
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  3. iVan on CSC 101

    Mark Rafn Guest

    iVan on CSC 101 <> wrote:
    >hi to all!....I'm really having having problms with this array
    >thing...our instructor just gave us 15 pages copy all about Arrays and
    >of course problms about it...I have 5 problems and really don't know
    >how to solve these.....geezzz.....they suck!...=D...hhmmmm...anyway
    >i'm here for any help from you guys...


    Thanks for honesty about asking homework questions. You may even get some
    help here, _IF_ you show that you've thought about the problem and are stuck
    on a specific thing, rather than not knowing where to start and being too lazy
    to try.

    >beginners like us really need ( I think) to have lectures by those who
    >should do it but I dunnot know why they're just giving us this stuff
    >without explanations...hhhhmmm....


    There's LOTS of books, and usually instructors are available to answer
    questions if you don't understand a problem.

    >1. Longest plateau. Given an array of integers, find the length and
    >location of the longest contiguous sequence of
    > equal values.


    I give this as an interview question sometimes. It's a good quickie to make
    sure the candidate can think somewhat clearly about a problem and handle basic
    coding.

    >2. Bad shuffling.


    I don't like this as an interview question (though something similar is not
    uncommon, I don't think it's that diagnostic). It's a pretty decent homework
    problem, though.

    >3. Scheduling with deadline.


    Interesting. Haven't seen this one, but I kind of like it. He shouldn't have
    given the hint, though.

    >4. Magic squares.


    Boring!

    > 5. US postal barcodes.


    I like having some real-world reference in the problem. Bonus points if you
    can figure out why there are 5 bars when 4 would do.

    >thank you so much for reading dude!


    Thanks you for posting! I look forward to hearing how you do!
    --
    Mark Rafn <http://www.dagon.net/>
     
    Mark Rafn, Feb 16, 2007
    #3
  4. iVan on CSC 101

    Lew Guest

    Mark Rafn wrote:
    iVan on CSC 101 <> wrote:
    >> 1. Longest plateau. Given an array of integers, find the length and
    >> location of the longest contiguous sequence of
    >> equal values.


    Have you learned loops, 'while', 'for' and 'do'?

    Let's backtrack. I will conclude from your choice of newsgroup that this is a
    Java assignment. You should know how to put together a Java class, for
    example, suppose your command line is parked at your project source directory.

    $ cat homework/QuestionOne.java
    package homework;
    public class QuestionOne
    {
    }

    $

    I like to show this as the file name above dashes, contents beneath:

    homework/QuestionOne.java
    --------------------------------
    package homework;
    /** Solution to Question One.
    */
    public class QuestionOne
    {
    /** Find and print the longest plateau
    * in an <code>int</code> array.
    * "plateau" definition per Prof. Genius.
    * @param ins <code>int []</code> to analyze.
    */
    public void showLongestPlateau( int [] ins )
    {
    for ( int value : ins )
    {
    }
    System.out.println( "And the answer is: " + 17 );
    }

    }

    Outside the loop you should declare some variables to hold the length and
    location of the plateau. Perhaps you should define a class to hold a pair of
    values for the length and location. You would use another pair of values (or
    an instance of your Pair class) to keep track of the current candidate for
    longest Plateau. Each time the next value in the array is different from the
    one you are tracking (is that a different variable?) you wrap up the length
    calculation and compare to the current longest candidate. A longer result is
    popped in to the "longest" variable(s), reinitialize your tracking
    variable(s), and start processing the new element.

    Thought.

    Thought is the key - think about the process of going through the array: what
    would you need to know to tell if you are in a plateau? Where would you store
    informtion about its length? Are there sub-parts to each loop iteration? What
    /must/ be true at the start and end of each loop iteration? What if there is
    more than one plateau of the longest length? Less than one?

    If you can write down a precise description of the process, which named items
    you must keep track of, how to change each one, and precisely what happens to
    them - then you can translate that into Java and Bob's your uncle.

    - Lew
     
    Lew, Feb 16, 2007
    #4
  5. iVan on CSC 101 wrote:
    > hi to all!....I'm really having having problms with this array
    > thing...our instructor just gave us 15 pages copy all about Arrays and
    > of course problms about it...I have 5 problems and really don't know
    > how to solve these.....geezzz.....they suck!...=D...hhmmmm...anyway
    > i'm here for any help from you guys...

    ....

    Have you done some easier array exercises? If not, I suggest doing so.

    These look to me like very good exercises for people who basically know
    how to use Java arrays, and need to merge arrays with algorithm
    thinking. They seem a bit too complicated for first array programs.

    Patricia
     
    Patricia Shanahan, Feb 16, 2007
    #5
  6. iVan on CSC 101

    Alex Hunsley Guest

    iVan on CSC 101 wrote:
    > hi to all!....I'm really having having problms with this array
    > thing...our instructor just gave us 15 pages copy all about Arrays and
    > of course problms about it...I have 5 problems and really don't know
    > how to solve these.....geezzz.....they suck!...=D...hhmmmm...anyway
    > i'm here for any help from you guys...
    >
    > beginners like us really need ( I think) to have lectures by those who
    > should do it but I dunnot know why they're just giving us this stuff
    > without explanations...hhhhmmm....


    Remember that 15 pages about arrays etc. you said you were given in the
    first paragraph? I presume that's the 'explanations' that you're
    complaining about not having. Can you read? It looks like you can...

    >
    > nyways, here are the problems about Arrays....


    Have you even attempted the problems? Or did you expect to just be able
    to pop into a homework help desk (which this place *isn't*) and just get
    given the answers?

    > thank you so much for reading dude!.....hoping for your positive
    > response.....badly needing it for our midterms....


    If you need it badly, then why not make a start on the problems, or ask
    specific questions?


    > you could also email me at ....thanks a
    > lot!...... ^ ^


    No, newsgroups work best when answers come here, not to personal emails.
     
    Alex Hunsley, Feb 16, 2007
    #6
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