Thread: Characters from String in alphabetic order using quicksort

Hi,
I am trying to do a program that takes all of the chars from a string and orders them in alphabetical order. It works fine, but when a is a last letter of a string it isn't being sorted.
Example: bcba = bbca, omnibus = bimnous (here u is in wrong place)
Here is my code:

public class sorty{
public static void sort(char[] a, int low, int high){
  int i = low;
  int j = high;
  if (j - i < 2) return;
  int m = (j+i)/2;
  char p = a[m];
  a[m] = a[i];
  a[i] = p;
 
  int r = i+1;
  for(int s = r; s!=j; s=s+1)
  {
    if(a[s]<p)
    {
      char tmp = a[s];
      a[s] = a[r];
      a[r] = tmp;
      r = r+1;
    }
  }
  r = r-1;
  a[i] = a[r];
  a[r] = p;
  sort(a,i,r);
  sort(a,r+1,j);
}
public Character[] toCharArray( String s )
{
   int len = s.length();
   Character[] array = new Character[len];
   for (int i = 0; i < len ; i++) {
      array[i] = new Character(s.charAt(i));
   }
   return array;
}
    public static void main(String[] args)
    {
        String input = "bcba";
        String output = quicksort(input);
        System.out.print(output);
    }
    public static String quicksort(String y)
    {
        int length = y.length();
        int i = 0;
        int j = length-1;
        char[] a = y.toCharArray();
        sort(a,i,j);
        String x=new String(a);
        return x;
 
    }
}

What do you mean by that?

When code doesn't work I try to run it through a program called Jeliot, but this time it crashes when it gets to the line char p = a[m]; in sort method so I can't really see what is going on after.

When my input is : omnibusa (I added extra a at the end) outcome is = bimnosua (letter a has not been sorted, but u has)

I have also tried this sorting method and it works with short strings, but when String has many characters, for example 2*(english alphabet) Input = abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwx yz my output is : aabcdefghijklbcdefghi....wwxxyyzz. It started with aab which is correct, but then it doesn't really sort until the letter w.

public static void sort(char[] a, int low, int high){
 
    int i = low;
    int j = high;
    char tmp;
 
    int pivot = (low+high)/2;
 
    while (i <= j) {
      while(a[i] < a[pivot]){
        i++;
      }
      while(a[j] > a[pivot]){
        j--;
      }
 
      if(i <= j) {
        tmp = a[i];
        a[i] = a[j];
        a[j] = tmp;
        i++;
        j--;
      }
    }
 
    if(low < j){
      sort(a, low, j);
    }
    if(i < high){
      sort(a,i,high);
    }
  }

The second sort method that I uploaded works for example with words : omnibus = bimnosu, omnibusa = abimnosu, Norm = Nmor, norm = mnor or even iamtiredofit = adefiiimortt
You are right about first one. It never fully works. It needs some corrections probably. Let's maybe stick to the second method?

P.S.: First method works with abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwx yz ... but second does not.

I created new sort method, but it doesn't work with string that has many letters in it. For example : abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwx yz doesn't work, but words such as omnibus, omnibusa etc. fully work.
So no.. I didn't solve it yet.
My new code:

public class sorty{
public static void sort(char[] a, int low, int high){
 
    int i = low;
    int j = high;
    char tmp;
 
    int pivot = i+(j-i)/2;
 
    while (i <= j) {
      while(a[i] < a[pivot]){
        i++;
      }
      while(a[j] > a[pivot]){
        j--;
      }
 
      if(i <= j) {
        tmp = a[i];
        a[i] = a[j];
        a[j] = tmp;
        i++;
        j--;
      }
    }
 
    if(low < j){
      sort(a, low, j);
    }
    if(i < high){
      sort(a,i,high);
    }
  }
public Character[] toCharArray( String s )
{
   int len = s.length();
   Character[] array = new Character[len];
   for (int i = 0; i < len ; i++) {
      array[i] = new Character(s.charAt(i));
   }
   return array;
}
    public static void main(String[] args)
    {
        String input = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz";
        String output = quicksort(input);
        System.out.print(output);
    }
    public static String quicksort(String y)
    {
        int length = y.length();
        int i = 0;
        int j = length-1;
        char[] a = y.toCharArray();
        sort(a,i,j);
        String x=new String(a);
        return x;
 
    }
}

Any solution? I tried to debug in eclipse it, but I am new to java so I don't really know how to use it (I tried to read about debugging and watch some vidoes on youtube).