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Thread: Your input with written code (Sorting and searching within array)

  1. #1
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    Default Your input with written code (Sorting and searching within array)

    So here's the assignment I was given:
    Writing a method that receives an int array titled values.
    the method has to return True, if throughout the array, there's an int that exists only once, or return false otherwise.
    Example : for an array 3,1,4,1,4,1 the method returns True
    for an array 3,1,4,1,4,3 method returns false.
    The received array is not sorted

    Here's my code


    public boolean single(int[] values) {
    boolean existsOnce = false;
     
    if(values.length == 1)
    return existsOnce = true;
    quicksort(values,0,(values.length -1));
     
    int counter = 0;
    int tempNumber = values[0];
    for(int i =0; i < values.length; )
    {
    if(tempNumber == values[i]){
    i++;
    counter ++;
    }
    else{
    if(counter == 1 || i == (values.length -1) )
    return existsOnce = true;
    else
    {
    tempNumber = values[i];
    counter= 0;
    }
    }
     
    }
    return existsOnce ;
    }

    Do you guys see any way of making this more efficient. also what would the "Big O" be? The class was about efficiency and that's what this method is supposed to strive for.


    Thanks!

    Gal
    Last edited by GalBenH; January 9th, 2012 at 01:18 PM.


  2. #2
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    Default Re: Your input with written code (Sorting and searching within array)

    Some words to the wise:

    Use indentation.
    Use brackets on every if and for, even if it's just one statement.
    Why: return existsonce = true;

    What do you think the "Big O" would be? Have you input different values of n to see how many iterations each takes?
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    Default Re: Your input with written code (Sorting and searching within array)

    //Removed some - as to not void Kevin's post
    An easier solution might be to used the Arrays utility class.
    Please use [highlight=Java]//code goes here...[/highlight] tags when posting your code

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    Default Re: Your input with written code (Sorting and searching within array)

    For what its worth, I do not see anywhere in the requirements that says the array should be sorted (yes, this is a hint in more ways than one)

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    Default Re: Your input with written code (Sorting and searching within array)

    Thanks all for your prompt help!
    Kevin,
    Regarding the existsOnce=true
    Before getting into any loop I wanted to eliminate the scenario of having an Array of only 1 int, which by deafult need this method to return True (for a single appearance of a specific int)


    newbie,
    I'm not supposed to use that as a part of the requirements.


    Copeg,

    That's an interesting approach, I was taking it for granted that a sorted array may make things simpler but it's definitely not a requirement.

    What do you think of this:


    public boolean single(int[] values) {
    boolean existsOnce = false;
    if(values.length == 1)
    return existsOnce = true;
     
    int counter = 0;
    int tempNumber = values[0];
    for(int i=0; i<values.length;i++){
      if(tempNumber == values[i]){
       counter ++;}
        else{
          if(counter == 1 || i == (values.length -1) )
          return existsOnce = true;
            else{
            tempNumber = values[i];
            counter= 0;}              
    }
    }
    return existsOnce ;
    }


    my main concern is that I'm not sure in this line:

    for(int i=0; i<values.length;i++){
    if(tempNumber == values[i]){
    counter ++;}

    If the tempNumber is progressed in ever step like the i is, in order to compare it the the remaining rest of the array in each step of the loop.

    I would love to see a sample correct solution from you guys (if possible) without making things too complicated (not supposed to be using advanced material).
    I actually learn a lot from these answers so please don't see it as a way of me trying to find an easy way out.
    My mind is drawing blank right now

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    Default Re: Your input with written code (Sorting and searching within array)

    counter ++;}
    Another comment on coding standards.
    Do NOT hide } on the same line with a statement.
    The ending } should be on a line by itself and in the same column as the statement line with the beginning {. That allows your eye to easily see the code structure and scope of variables.

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    Default Re: Your input with written code (Sorting and searching within array)

    Quote Originally Posted by GalBenH View Post
    Kevin,
    Regarding the existsOnce=true
    Before getting into any loop I wanted to eliminate the scenario of having an Array of only 1 int, which by deafult need this method to return True (for a single appearance of a specific int)
    So why not just return true?

    Quote Originally Posted by GalBenH View Post
    What do you think of this:


    public boolean single(int[] values) {
    boolean existsOnce = false;
    if(values.length == 1)
    return existsOnce = true;
     
    int counter = 0;
    int tempNumber = values[0];
    for(int i=0; i<values.length;i++){
      if(tempNumber == values[i]){
       counter ++;}
        else{
          if(counter == 1 || i == (values.length -1) )
          return existsOnce = true;
            else{
            tempNumber = values[i];
            counter= 0;}              
    }
    }
    return existsOnce ;
    }
    I'm honestly not really sure how that's supposed to solve your problem. Does it?


    Quote Originally Posted by GalBenH View Post
    I would love to see a sample correct solution from you guys (if possible) without making things too complicated (not supposed to be using advanced material).
    I actually learn a lot from these answers so please don't see it as a way of me trying to find an easy way out.
    My mind is drawing blank right now
    That's not really how this works. Does your solution work? If not, step through it with a debugger to see exactly what it's doing. Think about your approach- how would you do this in your head, without a computer? Really examine what you're actually doing in your head instead of saying "well I would just see if there were two numbers that are the same." How would you really do that? What if the list was a thousand numbers? How would you do it in your head or with a piece of paper and a pencil then?
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    Default Re: Your input with written code (Sorting and searching within array)

    I think I finally got it:



    public boolean single(int[] values)
    {
     
        if (values.length == 1)
        {
            return true;
        }
     
     
        for (int i=0; i<values.length; i++)
        {
            int counter = 0;
            int tempNumber = values[i];
     
            for (int j=0; j<values.length; j++)
            {
                if(tempNumber == values[j])
                {
                    counter++;
                }
     
                if (j == values.length && counter == 1)
                {
                    return true;
     
                }
                else {
                    return false
                }
            }
        }   
    }

    Do you guys approve?

  9. #9
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    Default Re: Your input with written code (Sorting and searching within array)

    Like I keep hinting at, it doesn't matter whether we approve. Does it do what you want? Do you understand how it works? Then don't worry about it.

    Actually, I don't see how this can possibly do what you described. Did you try running it with different inputs?
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  10. #10
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    Default Re: Your input with written code (Sorting and searching within array)

    Can you explain the logic for your code?
    For example:
    Why the counter?
    When in the search do you know that the condition you are looking for is true?

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