Java - my alphabetical order sorting algorithm not always working as expected

Question

Here's my java code. (Explanation at the end)

import java.util.Scanner;
import java.util.Arrays;
/**
 *
 * @author Laksh
 */
public class Sort4 {
    public static void Swap(int[] array,int Swap1,int Swap2){
        int temporarySwapper;
        temporarySwapper=array[Swap1];
        array[Swap1]=array[Swap2];
        array[Swap2]=temporarySwapper;
    }
    public static void Swap(String[] array,int Swap1,int Swap2){
        String temporarySwapper;
        temporarySwapper=array[Swap1];
        array[Swap1]=array[Swap2];
        array[Swap2]=temporarySwapper;
    }
    public static String[] alphasort(String[] original, int level, int start, int end ){
        int swaps;
        int[] array=new int[original.length];
        for(int i=0;i<original.length;i++){
            array[i]=(int)original[i].charAt(level);
        }
        do{
            swaps=0;
            for(int i=start;i<end;i++){
                if(array[i]>array[i+1]){
                    Swap(original,i,i+1);
                    Swap(array,i,i+1);
                    swaps++;
                }
            }
        }while(swaps != 0);
        return Arrays.copyOfRange(original, start, end+1);
    }
    public static String repeat(String s,int times){
        String returnString="";
        for(int i=0;i<times;i++){
            returnString+=s;
        }
        return returnString;
    }

        public static void main(String[] args) {
        Scanner input=new Scanner(System.in);        
        System.out.println("Enter 5 Names:");
        int max=Integer.MIN_VALUE;
        String[] name=new String[5];
        for(int i=0;i<5;i++){
            name[i]=input.next();
            if(name[i].length()>max){
                max=name[i].length();
            }
        }
        for(int i=0;i<5;i++){
            if(name[i].length()<max){
                name[i]=name[i]+repeat(" ",max-name[i].length());
            }
        }

        String[] sorted=alphasort(name,0,0,name.length-1);
        for(String c:sorted){
            System.out.println(c);
        }

    }

}

To Clarify the issues I am facing, my code relies on finding ascii integer value of a char, and then sorting an integer array. If the first letter of the string I am trying to is equal to the first of another, the code moves to the second letter, and so on. To avoid string index out of bounds, I used the "repeat" method to add enough spaces to the end of each string so that they are all the same length- as Strings of the same length would prevent this. The issue I am facing is that it sort correctly, but in some places, it fails.

for example, if I pass in "butter" and "butterfly", the two are outputed int he order they were entered, in relation to the other values, which are sorted properly! For example:

butter
cookie
butterfly
cookiemonster
ninja

sorts to

butter       
butterfly    
cookie       
cookiemonster
ninja

whereas

butterfly
cookie
butter
cookiemonster
ninja

sorts to

butterfly       
butter    
cookie       
cookiemonster
ninja

Help me, as I am unable to find my error.

There is no error. The output that you posted shows that both inputs are correctly sorted to the same output with butter coming before butterfly. — Erwin Bolwidt
– Erwin Bolwidt, Commented Mar 8, 2019 at 1:18
can you explain a bit more what's wrong with the output(sorted list)? — Lei Yang
– Lei Yang, Commented Mar 8, 2019 at 1:18
Oh, I'm sorry. I pasted the output incorrectly. It's been edited, so now you can see the issue with the 2nd output (1st was in fact correct) — Laksh illuminati
– Laksh illuminati, Commented Mar 8, 2019 at 1:33
Why don't you use TreeSet<String>() or RadixSort or Arrays.sort(original)? — Oleg Cherednik
– Oleg Cherednik, Commented Mar 8, 2019 at 13:17

gungor · Accepted Answer · 2019-03-08 09:10:47Z

1

You compared only first letters of each word and the order of words, butterfly and butter, didn't change.

You must compare each letter of each word with a function below:

  int size = myArray.length;

  for(int i = 0; i<size-1; i++) {
     for (int j = i+1; j<myArray.length; j++) {
        if(myArray[i].compareTo(myArray[j])>0) {
           String temp = myArray[i];
           myArray[i] = myArray[j];
           myArray[j] = temp;
        }
     }

edited Mar 8, 2019 at 9:10

gungor

4274 silver badges14 bronze badges

answered Mar 8, 2019 at 1:51

Renato Serra

212 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Java - my alphabetical order sorting algorithm not always working as expected

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related