本文共 8593 字，大约阅读时间需要 28 分钟。
所有内容均来自于：
以下总共给出了10种字符串hash函数，在上面的链接中可以找到各个Hash函数的描述，以及一些其它的关于hash函数的资料下载。
这些hash函数各自的优缺点不详。其中，ELFHash函数是在unix系统中被广泛使用的，也是《算法艺术与信息学竞赛》中作者推荐的一个字符串hash函数。DEKHash函数是Knuth在其《The Art of Computer Programming》第三卷中引入的。
关于其他算法文章请参考。
以下是C实现
unsigned int RSHash(char* str, unsigned int len) { unsigned int b = 378551; unsigned int a = 63689; unsigned int hash = 0; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash = hash * a + (*str); a = a * b; } return hash; } /* End Of RS Hash Function */ unsigned int JSHash(char* str, unsigned int len) { unsigned int hash = 1315423911; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash ^= ((hash << 5) + (*str) + (hash >> 2)); } return hash; } /* End Of JS Hash Function */ unsigned int PJWHash(char* str, unsigned int len) { const unsigned int BitsInUnsignedInt = (unsigned int)(sizeof(unsigned int) * 8); const unsigned int ThreeQuarters = (unsigned int)((BitsInUnsignedInt * 3) / 4); const unsigned int OneEighth = (unsigned int)(BitsInUnsignedInt / 8); const unsigned int HighBits = (unsigned int)(0xFFFFFFFF) << (BitsInUnsignedInt - OneEighth); unsigned int hash = 0; unsigned int test = 0; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash = (hash << OneEighth) + (*str); if((test = hash & HighBits) != 0) { hash = (( hash ^ (test >> ThreeQuarters)) & (~HighBits)); } } return hash; } /* End Of P. J. Weinberger Hash Function */ unsigned int ELFHash(char* str, unsigned int len) { unsigned int hash = 0; unsigned int x = 0; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash = (hash << 4) + (*str); if((x = hash & 0xF0000000L) != 0) { hash ^= (x >> 24); } hash &= ~x; } return hash; } /* End Of ELF Hash Function */ unsigned int BKDRHash(char* str, unsigned int len) { unsigned int seed = 131; /* 31 131 1313 13131 131313 etc.. */ unsigned int hash = 0; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash = (hash * seed) + (*str); } return hash; } /* End Of BKDR Hash Function */ unsigned int SDBMHash(char* str, unsigned int len) { unsigned int hash = 0; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash = (*str) + (hash << 6) + (hash << 16) - hash; } return hash; } /* End Of SDBM Hash Function */ unsigned int DJBHash(char* str, unsigned int len) { unsigned int hash = 5381; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash = ((hash << 5) + hash) + (*str); } return hash; } /* End Of DJB Hash Function */ unsigned int DEKHash(char* str, unsigned int len) { unsigned int hash = len; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash = ((hash << 5) ^ (hash >> 27)) ^ (*str); } return hash; } /* End Of DEK Hash Function */ unsigned int BPHash(char* str, unsigned int len) { unsigned int hash = 0; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash = hash << 7 ^ (*str); } return hash; } /* End Of BP Hash Function */ unsigned int FNVHash(char* str, unsigned int len) { const unsigned int fnv_prime = 0x811C9DC5; unsigned int hash = 0; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash *= fnv_prime; hash ^= (*str); } return hash; } /* End Of FNV Hash Function */ unsigned int APHash(char* str, unsigned int len) { unsigned int hash = 0xAAAAAAAA; unsigned int i = 0; for(i = 0; i < len; str++, i++) { hash ^= ((i & 1) == 0) ? ( (hash << 7) ^ (*str) * (hash >> 3)) : (~((hash << 11) + (*str) ^ (hash >> 5))); } return hash; } /* End Of AP Hash Function */ /* ************************************************************************** * * * General Purpose Hash Function Algorithms Library * * * * Author: Arash Partow - 2002 * * URL: http://www.partow.net * * URL: http://www.partow.net/programming/hashfunctions/index.html * * * * Copyright notice: * * Free use of the General Purpose Hash Function Algorithms Library is * * permitted under the guidelines and in accordance with the most current * * version of the Common Public License. * * http://www.opensource.org/licenses/cpl1.0.php * * * ***************************************************************************/class GeneralHashFunctionLibrary{ public long RSHash(String str) { int b = 378551; int a = 63689; long hash = 0; for(int i = 0; i < str.length(); i++) { hash = hash * a + str.charAt(i); a = a * b; } return hash; } /* End Of RS Hash Function */ public long JSHash(String str) { long hash = 1315423911; for(int i = 0; i < str.length(); i++) { hash ^= ((hash << 5) + str.charAt(i) + (hash >> 2)); } return hash; } /* End Of JS Hash Function */ public long PJWHash(String str) { long BitsInUnsignedInt = (long)(4 * 8); long ThreeQuarters = (long)((BitsInUnsignedInt * 3) / 4); long OneEighth = (long)(BitsInUnsignedInt / 8); long HighBits = (long)(0xFFFFFFFF) << (BitsInUnsignedInt - OneEighth); long hash = 0; long test = 0; for(int i = 0; i < str.length(); i++) { hash = (hash << OneEighth) + str.charAt(i); if((test = hash & HighBits) != 0) { hash = (( hash ^ (test >> ThreeQuarters)) & (~HighBits)); } } return hash; } /* End Of P. J. Weinberger Hash Function */ public long ELFHash(String str) { long hash = 0; long x = 0; for(int i = 0; i < str.length(); i++) { hash = (hash << 4) + str.charAt(i); if((x = hash & 0xF0000000L) != 0) { hash ^= (x >> 24); } hash &= ~x; } return hash; } /* End Of ELF Hash Function */ public long BKDRHash(String str) { long seed = 131; // 31 131 1313 13131 131313 etc.. long hash = 0; for(int i = 0; i < str.length(); i++) { hash = (hash * seed) + str.charAt(i); } return hash; } /* End Of BKDR Hash Function */ public long SDBMHash(String str) { long hash = 0; for(int i = 0; i < str.length(); i++) { hash = str.charAt(i) + (hash << 6) + (hash << 16) - hash; } return hash; } /* End Of SDBM Hash Function */ public long DJBHash(String str) { long hash = 5381; for(int i = 0; i < str.length(); i++) { hash = ((hash << 5) + hash) + str.charAt(i); } return hash; } /* End Of DJB Hash Function */ public long DEKHash(String str) { long hash = str.length(); for(int i = 0; i < str.length(); i++) { hash = ((hash << 5) ^ (hash >> 27)) ^ str.charAt(i); } return hash; } /* End Of DEK Hash Function */ public long BPHash(String str) { long hash = 0; for(int i = 0; i < str.length(); i++) { hash = hash << 7 ^ str.charAt(i); } return hash; } /* End Of BP Hash Function */ public long FNVHash(String str) { long fnv_prime = 0x811C9DC5; long hash = 0; for(int i = 0; i < str.length(); i++) { hash *= fnv_prime; hash ^= str.charAt(i); } return hash; } /* End Of FNV Hash Function */ public long APHash(String str) { long hash = 0xAAAAAAAA; for(int i = 0; i < str.length(); i++) { if ((i & 1) == 0) { hash ^= ((hash << 7) ^ str.charAt(i) * (hash >> 3)); } else { hash ^= (~((hash << 11) + str.charAt(i) ^ (hash >> 5))); } } return hash; } /* End Of AP Hash Function */} 转载地址：http://naoci.baihongyu.com/