Question

class test
 {
     static int arr[]={1,6,3,4,5,8,11};
     static int s=0,temp=0,e=0;
   public static void main(String [] args)throws Exception
   {
     QS(arr,0,arr.length-1);

    for(int i=0;i<arr.length;i++)
    System.out.print(arr[i]+"   ");

}

    public static void QS(int arr[] ,int i,int j)throws Exception
 {
int key=i;
int low=i+1;
int up=j;
int temp=0;
  System.out.println(key);   
 while(low<=up)
{
  do{
     low++;
    }while(arr[low]<arr[key]);

  do{
     up--;
    }while(arr[up]>arr[key]); 

 if(low<=up)
{   
   temp=arr[up];
   arr[up]=arr[low];
   arr[low]=temp;            
 }  
 }
   System.out.println(low+"++++"+up);

temp=arr[up];
arr[up]=arr[key];
arr[key]=temp;
if(0<up-1)        
      QS(arr,i,up-1);
if(low< arr.length-2)
      QS(arr,low,j);
   }
   }

Answer 1

Since this looks like homework, here is my advice:

After the partitioning step, print out your array together with the value and the position of the pivot, and verify visually that the partitioning has been done correctly. If it hasn’t been (as I suspect is the case), add some more print statements — or use a debugger — to understand where your program is going wrong.

Once the partitioning is working, move on to the recursion. This is comparatively easy: all you have to do is make sure that QS is calling itself with the correct i and j (both times), and that the base case is handled correctly.