Delete duplicate characters from string

Question

I'm trying to delete duplicate characters from a string. For example if I enter the string abaqueru it should give me bqer with duplicate characters a and u deleted. However, instead the result is an unnecessary loop. Here is the code:

public class question {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
   String s = "abaqueru";

   calculate(s);
    // TODO code application logic here
}

public static void calculate(String s){
     String result;

        for(int i = 0; i < s.length(); i++)
        {
           char c = s.charAt(i);
           char temp;
           temp=c;
           for(int j = 1; j < s.length(); j++)
                {

                   char x = s.charAt(j);
                   if(temp==x){
                       s=s.replaceAll(""+temp,"");
                       calculate(s);
                   }



                }

            System.out.println(s);
        }

}

don't change your question completely .ask new one if you have a another question — Madhawa Priyashantha
– Madhawa Priyashantha, Commented Aug 13, 2015 at 14:10

Jordi Castilla · Accepted Answer · 2015-08-13 14:05:13Z

7

String are immutable in java. After replaceall, you need to assign it back

s=s.replaceAll(""+temp,"");

If you didn't assign it back, the loop goes on forever.

That solves the stackoverflow error, I didn't concentrate on your actual logic :)

edited Aug 13, 2015 at 14:05

Jordi Castilla

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answered Aug 13, 2015 at 14:00

Suresh Atta

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1 Comment

Furkan Over a year ago

I corrected it thanks but i think i have algorithm problems also that taking me unnecessarry loops.

Madhawa Priyashantha · Accepted Answer · 2015-08-13 14:54:40Z

I will go with Suresh Atta's Answer which was leading to stack overflow error. I also checked your logic. Have made some necessary changes

public class Question {




    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
       String s = "abaqueru";

       calculate(s);
        // TODO code application logic here
    }

    public static void calculate(String s){
         String result;

            for(int i = 0; i < s.length(); i++)
            {
               char c = s.charAt(i);

               char temp;
               temp=c;
               for(int j = i+1; j < s.length(); j++)
                    {

                       char x = s.charAt(j);
                       if(temp==x){

                          s=s.replaceAll(""+temp, "");

                           break;
                         //  calculate(s);
                       }



                    }


            }

            System.out.println(s);

    }

}

However this can be further customized to achive performance in terms of space and time. Infact, more simpler logic can be used :)

daniel.caspers · Accepted Answer · 2015-08-13 14:13:50Z

1

Definitely go with Suresh Atta's answer! However, I figured I'd help glance over your code to help you find where some of your mistakes were.

I just glanced over your logic in the code though, and there is definitely some stuff worth glancing over. The most notable is that j is never used in the inner-for-loop. In fact, if you are using an IDE, it should warn you that j is never used.

UPDATE: Also, consider using String.valueOf(char c) instead of the s=s.replaceAll(""+temp,""); call you have in the if(temp==x) condition. That is, I assume that is so you could cast the character to a String? Then you can use String.append(), which you can read about on the link I sent you!

edited Aug 13, 2015 at 14:13

answered Aug 13, 2015 at 14:07

daniel.caspers

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4 Comments

Furkan Over a year ago

Yes, In there if i found any letter duplication in string, I change that duplicated letter with ""(space). and i use // ""+temp // for string parse

daniel.caspers Over a year ago

If you don't use j in the inner for loop, all 3 character variables will be the same. Notice that you are grabbing the same character each time through the inner for loop, thus comparing it to a character it is guaranteed to be equal to. In other words, you are grabbing the character (at location i) j times.

daniel.caspers Over a year ago

Also, any particular reason why you went with a recursive solution this way?

Furkan Over a year ago

I replace i with j in second loop and I dont know how many different repeated letter in string so i decide to use recursion.

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