Quick Sort Using Divide and Conquer

Algorithm

Partition(A,p,r)
{
    x=A[r]
    i=p-1
    for(j=p to r-1)
       {
        if(A[j]<=x){
        exchange A[i] with A[j]
     }
    }exchange A[i+1] with A[r]
      return i+1
   }
 Quick_Sort(A,p,r)
  {
       if(p<r)
        {
             int q= partition(A,p,r)
             Quick_Sort(A,p,q-1)
             Quick_Sort(A,q+1,r)
        }
}

Code

class quicksort{
    public static void main(String[] args) {
        int arr[]={3,2,1,5,8,1};
        quick_sort(arr,0,arr.length-1);
        for(int i:arr){
            System.out.print(i+" ");
        }
    }//r is the pivot
    static int partition(int arr[],int low,int r){
        int x=arr[r];
        int i=low-1;
        for(int j=low;j<r-1;j++){
            if(arr[j]<=x)
            {
                i++;
                int temp=arr[j];
                arr[j]=arr[i];
                arr[i]=temp;
            }
        }
        int temp=arr[r];
        arr[r]=arr[i+1];
        arr[i+1]=temp;
        return i+1;
    }
    static int[] quick_sort(int arr[],int low,int pivot)
    {
        if(low<pivot){
            int q=partition(arr, low, pivot);
            quick_sort(arr, low, q-1);
            quick_sort(arr,q+1,pivot);
        }
        return arr;
    }
}

Output

1 1 2 3 5 8