Quick Sort

package com.exuan.qsort;

//Time complexity
//average:O(N)
//best:O(NlogN)
//worst:O(N2)
public class QSort {
    public static void main(String[] args)
    {
        int[] data = {12,13,13,14,8,2,11,5,4,6,7,3,1,9,10,17,0};
        display(data);
        quickSort(data, 0, data.length -1);
        display(data);
    }
   
    /*quick sort the data from index x to index y
     * 1.appoint a pivot value(here the first index of data)
     * 2.find the first value which is less than the pivot from right to left, swap it with the pivot
     * 3.find the first value which is greater than the pivot from left to right, swap it with the pivot
     * Then after one round of quick sort, data will divided into two parts,
     * data left of pivot is less than pivot while data right of pivot is greater than key,
     * Note that we don't really need to do the swap, because the pivot always changes
     * recursive call quick sort
    */
    private static void quickSort(int[] data, int x, int y)
    {
        if(x >= y)
        {
            return;
        }
        int low = x;
        int high = y;
        int pivot = data[low];//pick a pivot value
        //one round of quick sort, data will divided into two parts
        while(low < high)
        {
            //find the first value which is less than the pivot from right to left
            while(low < high && data[high] >= pivot)
            {
                high--;
            }
            data[low] = data[high];//swap it with the pivot
           
            //find the first value which is greater than the pivot from left to right
            while(low < high && data[low] <= pivot)
            {
                low++;
            }
            data[high] = data[low];//swap it with the pivot
        }
        data[high] = pivot;//here we complete the real swap to assign the pivot
       
        //recursive call quick sort to sort the two parts
        quickSort(data, x, low - 1);
        quickSort(data, high + 1, y);
    }
   
    private static void display(int[] data)
    {
        for(int i = 0; i < data.length; i++)
        {
            System.out.print(data[i] + ",");
        }
        System.out.println();
    }
}