常见字符串哈希函数

最常用的两个：

 1          

 2 const int MAXN = 1000003;

 3 

 4 常用1

 5 1  SDBMHash

 6 int SDBMHash(char *str)

 7 {

 8     int hash = 0;

 9     while (*str) hash = (*str++) + (hash << 6) + (hash << 16) - hash;

10     return (hash & 0x7FFFFFFF) % MAXN;

11 }

12  

13 

14 常用2 

15 

16 int BKDRHash(char *str)

17 {

18     int seed = 131; 

19     int hash = 0;

20     while (*str) hash = hash * seed + (*str++);

21     return (hash & 0x7FFFFFFF) % MAXN;

22 }

最常见的8个：

  1 const int MAXN = 1000003;

  2 

  3 //常用 1

  4 1  SDBMHash

  5 unsigned int SDBMHash(char *str)

  6 {

  7     unsigned int hash = 0;

  8     while (*str)

  9     {

 10         // equivalent to: hash = 65599*hash + (*str++);

 11         hash = (*str++) + (hash << 6) + (hash << 16) - hash;

 12     }

 13     return (hash & 0x7FFFFFFF)%MAXN;

 14 }

 15  

 16 2  RS Hash Function

 17 unsigned int RSHash(char *str)

 18 {

 19     unsigned int b = 378551;

 20     unsigned int a = 63689;

 21     unsigned int hash = 0;

 22  

 23     while (*str)

 24     {

 25         hash = hash * a + (*str++);

 26         a *= b;

 27     }

 28     return (hash & 0x7FFFFFFF)%MAXN;

 29 }

 30  

 31 3 JS Hash Function

 32 unsigned int JSHash(char *str)

 33 {

 34     unsigned int hash = 1315423911;

 35  

 36     while (*str)

 37     {

 38         hash ^= ((hash << 5) + (*str++) + (hash >> 2));

 39     }

 40     return (hash & 0x7FFFFFFF)%MAXN;

 41 }

 42  

 43 4 P. J. Weinberger Hash Function

 44 unsigned int PJWHash(char *str)

 45 {

 46     unsigned int BitsInUnignedInt = (unsigned int)(sizeof(unsigned int) * 8);

 47     unsigned int ThreeQuarters    = (unsigned int)((BitsInUnignedInt  * 3) / 4);

 48     unsigned int OneEighth        = (unsigned int)(BitsInUnignedInt / 8);

 49     unsigned int HighBits         = (unsigned int)(0xFFFFFFFF) << (BitsInUnignedInt - OneEighth);

 50     unsigned int hash             = 0;

 51     unsigned int test             = 0;

 52     while (*str)

 53     {

 54         hash = (hash << OneEighth) + (*str++);

 55         if ((test = hash & HighBits) != 0)

 56         {

 57             hash = ((hash ^ (test >> ThreeQuarters)) & (~HighBits));

 58         }

 59     }

 60     return (hash & 0x7FFFFFFF)%MAXN;

 61 }

 62  

 63 5 ELF Hash Function

 64 unsigned int ELFHash(char *str)

 65 {

 66     unsigned int hash = 0;

 67     unsigned int x    = 0;

 68     while (*str)

 69     {

 70         hash = (hash << 4) + (*str++);

 71         if ((x = hash & 0xF0000000L) != 0)

 72         {

 73             hash ^= (x >> 24);

 74             hash &= ~x;

 75         }

 76     }

 77     return (hash & 0x7FFFFFFF)%MAXN;

 78 }

 79  

 80 //常用2 

 81 6 BKDR Hash Function

 82 unsigned int BKDRHash(char *str)

 83 {

 84     unsigned int seed = 131; // 31 131 1313 13131 131313 etc..

 85     unsigned int hash = 0;

 86     while (*str)

 87     {

 88         hash = hash * seed + (*str++);

 89     }

 90     return (hash & 0x7FFFFFFF)%MAXN;

 91 }

 92  

 93 7 DJB Hash Function

 94 unsigned int DJBHash(char *str)

 95 {

 96     unsigned int hash = 5381;

 97     while (*str)

 98     {

 99         hash += (hash << 5) + (*str++);

100     }

101     return (hash & 0x7FFFFFFF)%MAXN;

102 }

103  

104 8 AP Hash Function

105 unsigned int APHash(char *str)

106 {

107     unsigned int hash = 0;

108     int i;

109     for (i=0; *str; i++)

110     {

111         if ((i & 1) == 0)

112         {

113             hash ^= ((hash << 7) ^ (*str++) ^ (hash >> 3));

114         }

115         else

116         {

117             hash ^= (~((hash << 11) ^ (*str++) ^ (hash >> 5)));

118         }

119     }

120     return (hash & 0x7FFFFFFF)%MAXN;

121 }

原文链接：http://blog.csdn.net/cgl1079743846/article/details/7833794