常用字符串哈希函数(网上收集)
来源:互联网 发布:电子罗盘 数据 使用 编辑:程序博客网 时间:2024/05/09 18:40
http://zhktiger.blog.sohu.com/163971697.html
常用字符串哈希函数有BKDRHash,APHash,DJBHash,JSHash,RSHash,SDBMHash,PJWHash,ELFHash等等。经过测试,BKDRHash无论是在实际效果还是编码实现中,效果都是最突出的。APHash也是较为优秀的算法。DJBHash,JSHash,RSHash与SDBMHash各有千秋。PJWHash与ELFHash效果最差,但得分相似,其算法本质是相似的。
// SDB Hash Function
unsigned int SDBMHash(char *str)
{
unsigned int hash = 0;
while (*str)
{
// equivalent to: hash = 65599*hash + (*str++);
hash = (*str++) + (hash << 6) + (hash << 16) - hash;
}
return (hash & 0x7FFFFFFF);
}
// RS Hash Function
unsigned int RSHash(char *str)
{
unsigned int b = 378551;
unsigned int a = 63689;
unsigned int hash = 0;
while (*str)
{
hash = hash * a + (*str++);
a *= b;
}
return (hash & 0x7FFFFFFF);
}
// JS Hash Function
unsigned int JSHash(char *str)
{
unsigned int hash = 1315423911;
while (*str)
{
hash ^= ((hash << 5) + (*str++) + (hash >> 2));
}
return (hash & 0x7FFFFFFF);
}
// P. J. Weinberger Hash Function
unsigned int PJWHash(char *str)
{
unsigned int BitsInUnignedInt = (unsigned int)(sizeof(unsigned int) * 8);
unsigned int ThreeQuarters = (unsigned int)((BitsInUnignedInt * 3) / 4);
unsigned int OneEighth = (unsigned int)(BitsInUnignedInt / 8);
unsigned int HighBits = (unsigned int)(0xFFFFFFFF) << (BitsInUnignedInt - OneEighth);
unsigned int hash = 0;
unsigned int test = 0;
while (*str)
{
hash = (hash << OneEighth) + (*str++);
if ((test = hash & HighBits) != 0)
{
hash = ((hash ^ (test >> ThreeQuarters)) & (~HighBits));
}
}
return (hash & 0x7FFFFFFF);
}
// ELF Hash Function
unsigned int ELFHash(char *str)
{
unsigned int hash = 0;
unsigned int x = 0;
while (*str)
{
hash = (hash << 4) + (*str++);
if ((x = hash & 0xF0000000L) != 0)
{
hash ^= (x >> 24);
hash &= ~x;
}
}
return (hash & 0x7FFFFFFF);
}
// BKDR Hash Function
unsigned int BKDRHash(char *str)
{
unsigned int seed = 131; // 31 131 1313 13131 131313 etc..
unsigned int hash = 0;
while (*str)
{
hash = hash * seed + (*str++);
}
return (hash & 0x7FFFFFFF);
}
// DJB Hash Function
unsigned int DJBHash(char *str)
{
unsigned int hash = 5381;
while (*str)
{
hash += (hash << 5) + (*str++);
}
return (hash & 0x7FFFFFFF);
}
// AP Hash Function
unsigned int APHash(char *str)
{
unsigned int hash = 0;
int i;
for (i=0; *str; i++)
{
if ((i & 1) == 0)
{
hash ^= ((hash << 7) ^ (*str++) ^ (hash >> 3));
}
else
{
hash ^= (~((hash << 11) ^ (*str++) ^ (hash >> 5)));
}
}
return (hash & 0x7FFFFFFF);
}
- 常用字符串哈希函数(网上收集)
- 网上收集的asp.net常用js
- java自习网上常用资料收集
- PHP常用字符串函数收集(60个)
- Mysql字符串函数收集
- Java字符串函数收集
- 字符串处理函数收集
- 常用的字符串哈希函数
- 数据库常用函数收集
- 常用PHP函数收集
- 常用js函数收集
- 常用js函数收集
- 常用js函数收集
- VC常用函数收集
- 常用函数收集
- php 常用函数收集
- java常用函数收集
- 常用c函数收集
- Vim中的正则表达式
- switch分支
- 九度OJ 1003
- 动态规划 --- hdu 1176 **
- 山东理工大学ACM平台题答案 1170 C语言实验——最值
- 常用字符串哈希函数(网上收集)
- ubuntu启动流程及定制
- POJ 2155 Matrix(二维树状数组)
- AJAX状态值与状态码
- linux:vi 替换命令
- HDU 4612 桥数-缩点后树的直径
- sublime python的一些使用命令
- 考试系统——可输入并自动匹配的下拉框(三)——Html,Web控件级联
- uva--401 Palindromes