测一下Hashtable的排序规则

表面上是无规律的，实际上还是有规律的。

 

using System;using System.Collections;class MyClass{ static readonly int[] primes = { 3, 7, 11, 17, 23, 29, 37, 47, 59, 71, 89, 107, 131, 163, 197, 239, 293, 353, 431, 521, 631, 761, 919, 1103, 1327, 1597, 1931, 2333, 2801, 3371, 4049, 4861, 5839, 7013, 8419, 10103, 12143, 14591, 17519, 21023, 25229, 30293, 36353, 43627, 52361, 62851, 75431, 90523, 108631, 130363, 156437, 187751, 225307, 270371, 324449, 389357, 467237, 560689, 672827, 807403, 968897, 1162687, 1395263, 1674319, 2009191, 2411033, 2893249, 3471899, 4166287, 4999559, 5999471, 7199369 }; static int GetHashcode(object key, int k, int hashsize) { //Hk(key) = [GetHash(key) + k * (1 + (((GetHash(key) >> 5) + 1) % (hashsize – 1)))] % hashsize int k_code = key.GetHashCode(); return Math.Abs(k_code + k * (1 + (((k_code >> 5) + 1) % (hashsize - 1)))) % hashsize; } static void Print(Hashtable hs) { Console.WriteLine("============Hashtable Test================="); foreach (string key in hs.Keys) { Console.WriteLine("Hk(key):{0:0000},Key:{1}", GetHashcode(key, 1, 7), key); } } static void Main(string[] args) { //public Hashtable(int capacity, float loadFactor); //Hashtable hs = new Hashtable { 1, 2, 3, 4, 5, }; //测试C Hashtable hashC = new Hashtable(7); hashC.Add("5", "顺序1"); hashC.Add("1", "顺序1"); hashC.Add("6", "顺序2"); hashC.Add("4", "顺序2"); hashC.Add("3", "顺序3");//<-EndPos(操作完后移动到下一个位置,即"4") Print(hashC); Console.WriteLine("add all"); //0123456<==capacity(容量)=7 // 1 3456<==最后一次操作的下一位置 // ^^ // 4 5123<==指针移动顺序 hashC.Remove("0"); Print(hashC); Console.WriteLine("hashC.Remove('0');"); hashC.Remove("0"); Print(hashC); Console.WriteLine("hashC.Remove('0');"); hashC.Remove("4");//删除指针下移 Print(hashC); Console.WriteLine("hashC.Remove('4');"); hashC.Remove("0"); Print(hashC); Console.WriteLine("hashC.Remove('4');"); hashC.Add("2", "---");//添加不移动指针?!这次没动 Print(hashC); Console.WriteLine("hashC.Add('2');"); Console.ReadKey(); }}

 

结果如下：

============Hashtable Test=================
Hk(key):0004,Key:4
Hk(key):0005,Key:5
Hk(key):0006,Key:6
Hk(key):0001,Key:1
Hk(key):0003,Key:3
add all
============Hashtable Test=================
Hk(key):0004,Key:4
Hk(key):0005,Key:5
Hk(key):0006,Key:6
Hk(key):0001,Key:1
Hk(key):0003,Key:3
hashC.Remove('0');
============Hashtable Test=================
Hk(key):0004,Key:4
Hk(key):0005,Key:5
Hk(key):0006,Key:6
Hk(key):0001,Key:1
Hk(key):0003,Key:3
hashC.Remove('0');
============Hashtable Test=================
Hk(key):0005,Key:5
Hk(key):0006,Key:6
Hk(key):0001,Key:1
Hk(key):0003,Key:3
hashC.Remove('4');
============Hashtable Test=================
Hk(key):0005,Key:5
Hk(key):0006,Key:6
Hk(key):0001,Key:1
Hk(key):0003,Key:3
hashC.Remove('4');
============Hashtable Test=================
Hk(key):0005,Key:5
Hk(key):0006,Key:6
Hk(key):0001,Key:1
Hk(key):0002,Key:2
Hk(key):0003,Key:3
hashC.Add('2');

[1]测试了键值hashcode无冲突情况
[2]容量指定为第一个给定素数=7
[3]内部停留指针所在的位置：最后操作的位置向下移动一格
[4]Foreach时，从HeadPos开始，按顺序输出，容器可以看作一个环形队列
[5]字符的hashcode与Hk(key)完全一样

 

Hashcode分配规律:
[1]默认值的情况
3(素数表中的第一个情况)

 

[2]给定初始值的情况
如果给定初始值，它会在素数表中找比设置大小大的数的最小值。

 

[3]自然增长的情况
首个3，再表中取比这个数的两倍大的最小值，依次类推。

3->7->17->37->89->197->431->919->1931->4049->8419->17519->36353->75431->...

 

[4]给定初始值自然增长情况
参照[3],区别在于首字符的设定

[5]素数间隔
从23开始,后一个素数/前一个素数,约等于1.2