各种字符串Hash函数比较

寰子 — Tue, 14 Aug 2012 12:32:00 GMT

得分�W�一�Q?/p>

// 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);
}

得分�W�二�Q?/p>

// 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);
}

得分�W�三�Q?/p>

// DJB Hash Function
unsigned int DJBHash(char *str)
{
    unsigned int hash = 5381;

    while (*str)
    {
        hash += (hash << 5) + (*str++);
    }

    return (hash & 0x7FFFFFFF);
}

得分�W�四�Q?/p>

// JS Hash Function
unsigned int JSHash(char *str)
{
    unsigned int hash = 1315423911;

    while (*str)
    {
        hash ^= ((hash << 5) + (*str++) + (hash >> 2));
    }

    return (hash & 0x7FFFFFFF);
}

另外�Q�此处也有一��文章，其中提及了另外几�U�效率也颇高的hash��法

http://programmers.stackexchange.com/questions/49550/which-hashing-algorithm-is-best-for-uniqueness-and-speed/145633#145633

寰子 2012-08-14 20:32 发表评论

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各种字符串Hash函数比较