最差情况，序列刚好是有序的，复杂度为O(n^2)
最好情况，每次基准刚好是中间值，复杂度为O(nlogn)
平均复杂度为：O(nlogn) 不稳定的排序算法
由于递归，需要消耗运行时栈的空间
static int partition(int[] unsorted, int low, int high) {
int pivot = unsorted[low];
while (low < high) {
while (low < high && unsorted[high] > pivot) high--;
unsorted[low] = unsorted[high];
while (low < high && unsorted[low] <= pivot) low++;
unsorted[high] = unsorted[low];
}
unsorted[low] = pivot;
return low;
}
static void quick_sort(int[] unsorted, int low, int high) {
int loc = 0;
if (low < high) {
loc = partition(unsorted, low, high);
quick_sort(unsorted, low, loc - 1);
quick_sort(unsorted, loc + 1, high);
}
}
