Stable sort
    Before sorting [2, 9, 3, 4, 1, 5, 8, 1, 4, 8, 7, 6]
    After sorting  [1, 1, 2, 3, 4, 4, 5, 6, 7, 8, 8, 9]
Unstable sort
    Before sorting [2, 9, 3, 4, 1, 5, 8, 1, 4, 8, 7, 6]
    After sorting  [1, 1, 2, 3, 4, 4, 5, 6, 7, 8, 8, 9]