public class QuickSort {
    public static void main(String[] args) {
        int[] array = {4,6,2,14,12,36,5,95,41,75,11,21,14};
        for (int i : quickSort(array,0,args.length)) {
            System.out.print(i + " ");
        }
    }
    /**
     * 快速排序方法
     * @param array
     * @param start
     * @param end
     * @return
     */
    public static int[] quickSort(int[] array, int start, int end) {
        if (array.length < 1 || start < 0 || end >= array.length || start > end)
            return null;
        int smallIndex = partition(array, start, end);
        if (smallIndex > start)
            quickSort(array, start, smallIndex - 1);
        if (smallIndex < end)
            quickSort(array, smallIndex + 1, end);
        return array;
    }

    /**
     * 快速排序算法——partition
     * @param array
     * @param start
     * @param end
     * @return
     */
    private static int partition(int[] array, int start, int end) {
        int pivot = (int) (start + Math.random() * (end - start + 1));
        int smallIndex = start - 1;
        swap(array, pivot, end);
        for (int i = start; i <= end; i++)
            if (array[i] <= array[end]) {
                smallIndex++;
                if (i > smallIndex)
                    swap(array, i, smallIndex);
            }
        return smallIndex;
    }

    /**
     * 交换数组内两个元素
     * @param array
     * @param i
     * @param j
     */
    private static void swap(int[] array, int i, int j) {
        int temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }
}