Java排序算法 希尔排序

希尔排序(Shell Sort)是插入排序的一种。是针对直接插入排序算法的改进。该方法又称缩小增量排序，因DL．Shell于1959年提出而得名。本文主要介绍希尔排序用Java是怎样实现的。

AD：

希尔排序(缩小增量法) 属于插入类排序,是将整个无序列分割成若干小的子序列分别进行插入排序。希尔排序并不稳定，O(1)的额外空间，时间复杂度为O(N*(logN)^2)。最坏的情况下的执行效率和在平均情况下的执行效率相比相差不多。

基本思想：

先取一个小于n的整数d1作为第一个增量，把文件的全部记录分成d1个组。所有距离为d1的倍数的记录放在同一个组中。先在各组内进行直接插入排序；然后，取第二个增量d2<d1重复上述的分组和排序，直至所取的增量dt=1(dt<dt-l<…<d2<d1)，即所有记录放在同一组中进行直接插入排序为止。

代码实现：

1. public<wbr>class<wbr>Test<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr></wbr>
2. public<wbr>static<wbr>int[]<wbr></wbr></wbr></wbr>a<wbr>=<wbr>{<wbr>10,<wbr>32,<wbr>1,<wbr>9,<wbr>5,<wbr>7,<wbr>12,<wbr>0,<wbr>4,<wbr>3<wbr>};<wbr>//<wbr>预设数据数组<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
3. public<wbr>static<wbr>void<wbr>main(String<wbr>args[])<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
4. int<wbr>i;<wbr>//<wbr>循环计数变量<wbr><wbr></wbr></wbr></wbr></wbr></wbr>
5. int<wbr></wbr>Index<wbr>=<wbr></wbr></wbr>a.length;//<wbr>数据索引变量<wbr><wbr></wbr></wbr></wbr>
6. System.out.print("排序前:<wbr>");<wbr><wbr></wbr></wbr></wbr>
7. for<wbr>(</wbr>i<wbr>=<wbr></wbr></wbr>0;<wbr>i<wbr></wbr></wbr>&lt;<wbr></wbr>Index<wbr>-<wbr>1;<wbr>i++)<wbr><wbr></wbr></wbr></wbr></wbr></wbr>
8. System.out.printf("%3s<wbr>",<wbr>a);<wbr><wbr></wbr></wbr></wbr></wbr>
9. System.out.println("");<wbr><wbr></wbr></wbr>
10. ShellSort(Index<wbr>-<wbr>1);<wbr>//<wbr>选择排序<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
11. //<wbr>排序后结果<wbr><wbr></wbr></wbr></wbr>
12. System.out.print("排序后:<wbr>");<wbr><wbr></wbr></wbr></wbr>
13. for<wbr>(</wbr>i<wbr>=<wbr></wbr></wbr>0;<wbr>i<wbr></wbr></wbr>&lt;<wbr></wbr>Index<wbr>-<wbr>1;<wbr>i++)<wbr><wbr></wbr></wbr></wbr></wbr></wbr>
14. System.out.printf("%3s<wbr>",<wbr>a);<wbr><wbr></wbr></wbr></wbr></wbr>
15. System.out.println("");<wbr><wbr></wbr></wbr>
16. }<wbr><wbr></wbr></wbr>
17. public<wbr>static<wbr>void<wbr>ShellSort(int<wbr>Index)<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
18. int<wbr>i,<wbr>j,<wbr>k;<wbr>//<wbr>循环计数变量<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
19. int<wbr>Temp;<wbr>//<wbr>暂存变量<wbr><wbr></wbr></wbr></wbr></wbr></wbr>
20. boolean<wbr>Change;<wbr>//<wbr>数据是否改变<wbr><wbr></wbr></wbr></wbr></wbr></wbr>
21. int<wbr>DataLength;<wbr>//<wbr>分割集合的间隔长度<wbr><wbr></wbr></wbr></wbr></wbr></wbr>
22. int<wbr>Pointer;<wbr>//<wbr>进行处理的位置<wbr><wbr></wbr></wbr></wbr></wbr></wbr>
23. DataLength<wbr>=<wbr>(int)<wbr>Index<wbr>/<wbr>2;<wbr>//<wbr>初始集合间隔长度<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
24. while<wbr>(DataLength<wbr>!=<wbr>0)<wbr>//<wbr>数列仍可进行分割<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
25. {<wbr><wbr></wbr></wbr>
26. //<wbr>对各个集合进行处理<wbr><wbr></wbr></wbr></wbr>
27. for<wbr>(</wbr>j<wbr>=<wbr></wbr></wbr>DataLength;<wbr>j<wbr></wbr></wbr>&lt;<wbr></wbr>Index;<wbr>j++)<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr>
28. Change<wbr>=<wbr></wbr></wbr>false;<wbr><wbr></wbr></wbr>
29. Temp<wbr>=<wbr></wbr></wbr>a[j];<wbr>//<wbr>暂存Data[j]的值,待交换值时用<wbr><wbr></wbr></wbr></wbr></wbr>
30. Pointer<wbr>=<wbr></wbr></wbr>j<wbr>-<wbr>DataLength;<wbr>//<wbr>计算进行处理的位置<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
31. //<wbr>进行集合内数值的比较与交换值<wbr><wbr></wbr></wbr></wbr>
32. while<wbr>(Temp<wbr></wbr></wbr>&lt;<wbr></wbr>a[Pointer]<wbr>&amp;&amp;<wbr>Pointer<wbr></wbr></wbr></wbr>>=<wbr>0<wbr>&amp;&amp;<wbr>Pointer<wbr></wbr></wbr></wbr></wbr>&lt;=<wbr>Index)<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr>
33. a[Pointer<wbr>+<wbr>DataLength]<wbr>=<wbr>a[Pointer];<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
34. //<wbr>计算下一个欲进行处理的位置<wbr><wbr></wbr></wbr></wbr>
35. PointerPointer<wbr>=<wbr>Pointer<wbr>-<wbr>DataLength;<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
36. Change<wbr>=<wbr></wbr></wbr>true;<wbr><wbr></wbr></wbr>
37. if<wbr>(Pointer<wbr></wbr></wbr>&lt;<wbr></wbr>0<wbr>||<wbr>Pointer<wbr></wbr></wbr></wbr>><wbr>Index)<wbr><wbr></wbr></wbr></wbr>
38. break;<wbr><wbr></wbr></wbr>
39. }<wbr><wbr></wbr></wbr>
40. //<wbr>与最后的数值交换<wbr><wbr></wbr></wbr></wbr>
41. a[Pointer<wbr>+<wbr>DataLength]<wbr>=<wbr>Temp;<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
42. if<wbr>(Change)<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr>
43. //<wbr>打印目前排序结果<wbr><wbr></wbr></wbr></wbr>
44. System.out.print("排序中:<wbr>");<wbr><wbr></wbr></wbr></wbr>
45. for<wbr>(</wbr>k<wbr>=<wbr></wbr></wbr>0;<wbr>k<wbr></wbr></wbr>&lt;<wbr></wbr>Index;<wbr>k++)<wbr><wbr></wbr></wbr></wbr>
46. System.out.printf("%3s<wbr>",<wbr>a[k]);<wbr><wbr></wbr></wbr></wbr></wbr>
47. System.out.println("");<wbr><wbr></wbr></wbr>
48. }<wbr><wbr></wbr></wbr>
49. }<wbr><wbr></wbr></wbr>
50. DataLengthDataLength<wbr>=<wbr>DataLength<wbr>/<wbr>2;<wbr>//<wbr>计算下次分割的间隔长度<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
51. }<wbr><wbr></wbr></wbr>
52. }<wbr><wbr></wbr></wbr>
53. }<wbr></wbr>

希尔排序几乎没有最坏情况，无论是正序、逆序、乱序，所用时间都不是很多，附加储存是O(1)，的确非常不错。在没搞清楚快速排序、堆排序之前，它的确是个很好的选择。希望能给你带来帮助。