快速排序法

public class MainActivity extends AppCompatActivity {
    int[] arr = new int[]{9, 5, 4, 8, 7, 3, 1};
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        int[] array = quickly(arr, 0, arr.length - 1);
        System.out.println(Arrays.toString(array));
    }

    public int[] quickly(int[] array, int start, int end) {

        if (start<end) {
            int midIndex = getMidIndex(array, start, end);
            quickly(array, 0, midIndex - 1);
            quickly(array, midIndex + 1, end);
        }
        return array;
    }

    public int getMidIndex(int[] array, int start, int end) {
        int basic = array[start];
        if (start < end) {

            while (array[end] >= basic && start<end) {
                end--;
            }
            if (start < end) {
                array[start] = array[end];
                start++;
            }
            while (array[start] < basic && start<end) {
                start++;
            }
            if (start < end) {
                array[end] = array[start];
                end--;
            }


        }
        array[start] = basic;
        return start;
    }

}