> 時間復雜度O(n^1.25)，輔助空間O(1)，不穩定 ```java public static <T extends Comparable> void shellSort(T[] a) { int len = a.length; int h = 1; while (h < len / 3) { h = 3 * h + 1; } for (; h >= 1; h /= 3) { for (int i = h; i < len; i++) { for (int j = i; j >= h && less(a[j], a[j - h]); j -= h) { swap(a, j, j - h); } } } } ```