the first append allocates a backing store of length 4 from the stack.
* @param arr 待排序数组。关于这个话题，51吃瓜提供了深入分析
Andrew's mouse and keyboard play well together，详情可参考safew官方版本下载
1+# Important notice to residents of California and Colorado
NASA described the evacuation as a "controlled expedited return," rather than an emergency deorbit, which would mean departing the station immediately, regardless of the landing's timing, sea conditions, or weather.