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Thread: binarySearch troubles

  1. #1
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    Default binarySearch troubles

    Hi,
    Im making a program that scrambles a word into all the possible permutations. So i swap letters in the string randomly to make a new string. I then want to search the array to see if that string allready exist in the array, however when i use binarySearch it says it cannot find the method. Here is my code:

    import java.util.Arrays;
    import java.util.Random;
    import java.lang.StringBuilder;
    public class StringScramble
    {
     
        public static void main (String[] args)
        {
        StringBuffer myString = new StringBuffer ("abc");
        int length = myString.length();
        int permu = 1;
        Random randomGenerator = new Random();
     
        while (length > 1){
            permu *= length;
            length--;
            System.out.println(permu);
            }
     
        int arrayNum = 0;        
        String[] array = new String[permu];
        array[arrayNum] = myString.toString();
        arrayNum++;
     
            while(arrayNum < permu){
                //initialize variables
                int length2 = myString.length();
                int randomInt1 = randomGenerator.nextInt(length2);
                char swap1 = myString.charAt(randomInt1);
                int randomInt2 = randomGenerator.nextInt(length2);
                char swap2 = myString.charAt(randomInt2);
                char temp;
     
                //the switch
                temp = swap1;
                swap1=swap2;
                swap2=temp;
     
                //set it in the string
                myString.setCharAt(randomInt1, swap1);
                myString.setCharAt(randomInt2, swap2);
     
                int search = array.binarySearch(array, myString.toString());
     
                if (!(search>=0)){
                array[arrayNum]= myString.toString();
                arrayNum++;
            }
        }
    }
    }

    Also, if someone knows of a easier way to find permutations, that would be helpful too

    Thanks
    Joel


  2. #2
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    Default Re: binarySearch troubles

    The only methods an array has is the ones it inherits from Object. Looking! Looking! Nope. Object does not have a binarySearch method. You can either write the method yourself or you can take a look at the Arrays class.
    Improving the world one idiot at a time!

  3. #3
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    Default Re: binarySearch troubles

    Hey,
    I made a new method for it:
    import java.util.Arrays;
    import java.util.Random;
    import java.lang.StringBuilder;
    public class StringScramble
    {
     
        public static void main (String[] args)
        {
        StringBuffer myString = new StringBuffer ("abc");
        int length = myString.length();
        int permu = 1;
        Random randomGenerator = new Random();
     
        while (length > 1){
            permu *= length;
            length--;
            System.out.println(permu);
            }
     
        int arrayNum = 0;        
        String[] array = new String[permu];
        array[arrayNum] = myString.toString();
        arrayNum++;
     
            while(arrayNum < permu){
                //initialize variables
                int length2 = myString.length();
                int randomInt1 = randomGenerator.nextInt(length2);
                char swap1 = myString.charAt(randomInt1);
                int randomInt2 = randomGenerator.nextInt(length2);
                char swap2 = myString.charAt(randomInt2);
                char temp;
     
                //the switch
                temp = swap1;
                swap1=swap2;
                swap2=temp;
     
                //set it in the string
                myString.setCharAt(randomInt1, swap1);
                myString.setCharAt(randomInt2, swap2);
     
                int search = checkArray(array, myString.toString(), permu);
     
                if (search>0){
                array[arrayNum]= myString.toString();
                arrayNum++;
            }
        }
            System.out.println(array[0]);
            System.out.println(array[1]);
            System.out.println(array[2]);
            System.out.println(array[3]);
            System.out.println(array[4]);
            System.out.println(array[5]);
     
    }
     
        public static int checkArray(String[] array, String checkee, int permu){
            int counter = 0;
            int returner=0;
                    System.out.println(array[0]);
            System.out.println(array[1]);
            System.out.println(array[2]);
            System.out.println(array[3]);
            System.out.println(array[4]);
            System.out.println(array[5]);
            while (counter<permu){
                if (checkee != array[counter]){
                   returner++;
                }
                counter++;
                }
            System.out.println("Returner:"+returner);
            return returner;
            }
    }

    However, each time it adds to counter, even if it is equal to the value. How can i fix this?
    Joel

  4. #4
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    Default Re: binarySearch troubles

    What is the actual problem? Where is the problem?
    You must provide SSCE
    Last edited by Mr.777; November 3rd, 2011 at 08:45 AM.

  5. #5
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    Default Re: binarySearch troubles

    So, the method checks to see if the string matches with a slot in the array, or array[counter]. If the string and the array slot are not equal, it adds 1 to the value that gets returned. If the value that gets returned is greater than 0, then it adds the new permutation to the array... i realize this is kindof a spaghetti code...

  6. #6
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    Default Re: binarySearch troubles

    My problem is, that in the method that checks if the string matches the array slot, it adds 1 to the return value, even if it is equal to it... So it will always add it to the array even though its already in it...
    public static int checkArray(String[] array, String checkee, int permu){
            int counter = 0;
            int returner=0;
            while (counter<permu){
                if (checkee != array[counter]){
                   returner++;
                }
                counter++;
                }
            System.out.println("Returner:"+returner);
            return returner;
            }
    }

  7. #7
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    Default Re: binarySearch troubles

    Did you try debugging this part of your code?

  8. #8
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    Default Re: binarySearch troubles

    No, how do i do that? (I use BlueJ, btw)

  9. #9
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    Default Re: binarySearch troubles

    Well, you read your IDE documentation or if you can't find, try using System.out.println() after consecutive statements and try to find where actually the problem is.

  10. #10
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    Default Re: binarySearch troubles

    ThankYou, I figured out what was wrong with it.

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