Quick Sort

/*
Sort an array A using Quick Sort. Change in the input array itself. So no need to return or print anything.

Input format :
Line 1 : Integer n i.e. Array size
Line 2 : Array elements (separated by space)

Output format :
Array elements in increasing order (separated by space)

Constraints :
1 <= n <= 10^3

Sample Input 1 :
6 
2 6 8 5 4 3
Sample Output 1 :
2 3 4 5 6 8

Sample Input 2 :
5
1 5 2 7 3
Sample Output 2 :
1 2 3 5 7 
*/


public class Solution {
	
	public static void quickSort(int[] input) {
		/* Your class should be named Solution
		 * Don't write main().
		 * Don't read input, it is passed as function argument.
		 * No need to print or return the output.
		 * Taking input and printing output is handled automatically.
		 */
        
        quickSort(input,0,input.length-1);	
	}
    
    public static void quickSort(int[] input, int si, int ei)
    {
        if (si>=ei)
        {
            return;
        }
        int pivotIndex=partition(input,si,ei);
        quickSort(input, si, pivotIndex-1);
        quickSort(input,pivotIndex+1,ei);
    }
    
    public static int partition(int[] a, int si, int ei)
    {
        int pivotElement=a[si];
        int smallerEleCount=0;
        for(int i=si+1;i<=ei;i++)
        {
            if (a[i]<pivotElement)
            {
                smallerEleCount++;
            }
        }
        
        int temp=a[si+smallerEleCount];
        a[si+smallerEleCount]=pivotElement;
        a[si]=temp;
        
        int i=si;
        int j=ei;
        while(i<j)
        {
            if (a[i]<pivotElement)
            {
                i++;
            }
            else if (a[j]>=pivotElement)
            {
                j--;
            }
            else
            {
                temp=a[i];
                a[i]=a[j];
                a[j]=temp;
                i++;
                j--;
            }
        }
        
        return si+smallerEleCount;
    }
	
}