[数据结构]适用于字符串的Hash函数

来源：互联网发布：修道士和野人问题java 编辑：程序博客网时间：2024/05/16 15:51
unsigned int RSHash(const std::string& str){   unsigned int b    = 378551;   unsigned int a    = 63689;   unsigned int hash = 0;   for(std::size_t i = 0; i < str.length(); i++)   {      hash = hash * a + str[i];      a    = a * b;   }   return hash;}/* End Of RS Hash Function */unsigned int JSHash(const std::string& str){   unsigned int hash = 1315423911;   for(std::size_t i = 0; i < str.length(); i++)   {      hash ^= ((hash << 5) + str[i] + (hash >> 2));   }   return hash;}/* End Of JS Hash Function */unsigned int PJWHash(const std::string& str){   unsigned int BitsInUnsignedInt = (unsigned int)(sizeof(unsigned int) * 8);   unsigned int ThreeQuarters     = (unsigned int)((BitsInUnsignedInt  * 3) / 4);   unsigned int OneEighth         = (unsigned int)(BitsInUnsignedInt / 8);   unsigned int HighBits          = (unsigned int)(0xFFFFFFFF) << (BitsInUnsignedInt - OneEighth);   unsigned int hash              = 0;   unsigned int test              = 0;   for(std::size_t i = 0; i < str.length(); i++)   {      hash = (hash << OneEighth) + str[i];      if((test = hash & HighBits)  != 0)      {         hash = (( hash ^ (test >> ThreeQuarters)) & (~HighBits));      }   }   return hash;}/* End Of  P. J. Weinberger Hash Function */unsigned int ELFHash(const std::string& str){   unsigned int hash = 0;   unsigned int x    = 0;   for(std::size_t i = 0; i < str.length(); i++)   {      hash = (hash << 4) + str[i];      if((x = hash & 0xF0000000L) != 0)      {         hash ^= (x >> 24);      }      hash &= ~x;   }   return hash;}/* End Of ELF Hash Function */unsigned int BKDRHash(const std::string& str){   unsigned int seed = 131; // 31 131 1313 13131 131313 etc..   unsigned int hash = 0;   for(std::size_t i = 0; i < str.length(); i++)   {      hash = (hash * seed) + str[i];   }   return hash;}/* End Of BKDR Hash Function */unsigned int SDBMHash(const std::string& str){   unsigned int hash = 0;   for(std::size_t i = 0; i < str.length(); i++)   {      hash = str[i] + (hash << 6) + (hash << 16) - hash;   }   return hash;}/* End Of SDBM Hash Function */unsigned int DJBHash(const std::string& str){   unsigned int hash = 5381;   for(std::size_t i = 0; i < str.length(); i++)   {      hash = ((hash << 5) + hash) + str[i];   }   return hash;}/* End Of DJB Hash Function */unsigned int DEKHash(const std::string& str){   unsigned int hash = static_cast<unsigned int>(str.length());   for(std::size_t i = 0; i < str.length(); i++)   {      hash = ((hash << 5) ^ (hash >> 27)) ^ str[i];   }   return hash;}/* End Of DEK Hash Function */unsigned int BPHash(const std::string& str){   unsigned int hash = 0;   for(std::size_t i = 0; i < str.length(); i++)   {      hash = hash << 7 ^ str[i];   }   return hash;}/* End Of BP Hash Function */unsigned int FNVHash(const std::string& str){   const unsigned int fnv_prime = 0x811C9DC5;   unsigned int hash = 0;   for(std::size_t i = 0; i < str.length(); i++)   {      hash *= fnv_prime;      hash ^= str[i];   }   return hash;}/* End Of FNV Hash Function */unsigned int APHash(const std::string& str){   unsigned int hash = 0xAAAAAAAA;   for(std::size_t i = 0; i < str.length(); i++)   {      hash ^= ((i & 1) == 0) ? (  (hash <<  7) ^ str[i] * (hash >> 3)) :                               (~((hash << 11) + (str[i] ^ (hash >> 5))));   }   return hash;}/* End Of AP Hash Function */
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