Question

我需要计算一组整数的哈希值，这些整数的顺序是感兴趣的主题。整数可能很多，所以我想总结一下！具体来说，我用c ++编写代码。对于简单算法的任何建议都表示赞赏。

Answer 1

假设你想要输出一个整数，你可能会比以下更糟糕（并且更好，但至少它很简单）：

unsigned int hash = 0;

for each int i   // not sure how you're storing them
{
  hash = ((31 * hash) + (unsigned)i);
}

如果您的整数是i_1，... i_n则计算

31^n * i_1 + 31^(n-1) * i_2 + ... + 31 * i_(n-1) + i_n

即。订单很重要。

转换为无符号类型提供了定义的溢出行为，而不是未定义的行为（在任何速率下都是C;不确定C ++是否在我的头顶）。

这是一个相当标准的算法，我认为是由Sedgewick描述的。

（挑选，但如果订单很重要，那么你就没有一套。）

Answer 2

您可以使用CRC功能。这是一个64位的实现。

标题信息：

typedef unsigned long long DWORD64 //maybe this is needed

inline void InitCRC64(DWORD64 &crc)
{
  crc = 0xFFFFFFFFFFFFFFFFULL;
}

extern const DWORD64 crctab64[256];
/**
 * CRC64 function
 *
 * @param[in] data pointer to the buffer
 * @param[in] len length of buffer in bytes
 * @param[in,out] hash in = initial value of the hash; out = returned hash
 */
inline void GetCRC64(DWORD64 &crc, const unsigned char *cp, unsigned long length)
{
  while (length--)
    crc = crctab64[(crc ^ *(cp++)) & 0xff] ^ (crc >> 8);
}

源文件：

/*
 * poly 0x95AC9329AC4BC9B5ULL and init 0xFFFFFFFFFFFFFFFFULL
 */
const DWORD64 crctab64[256] = {
  0x0000000000000000ULL, 0x7ad870c830358979ULL, 0xf5b0e190606b12f2ULL,
  0x8f689158505e9b8bULL, 0xc038e5739841b68fULL, 0xbae095bba8743ff6ULL,
  0x358804e3f82aa47dULL, 0x4f50742bc81f2d04ULL, 0xab28ecb46814fe75ULL,
  0xd1f09c7c5821770cULL, 0x5e980d24087fec87ULL, 0x24407dec384a65feULL,
  0x6b1009c7f05548faULL, 0x11c8790fc060c183ULL, 0x9ea0e857903e5a08ULL,
  0xe478989fa00bd371ULL, 0x7d08ff3b88be6f81ULL, 0x07d08ff3b88be6f8ULL,
  0x88b81eabe8d57d73ULL, 0xf2606e63d8e0f40aULL, 0xbd301a4810ffd90eULL,
  0xc7e86a8020ca5077ULL, 0x4880fbd87094cbfcULL, 0x32588b1040a14285ULL,
  0xd620138fe0aa91f4ULL, 0xacf86347d09f188dULL, 0x2390f21f80c18306ULL,
  0x594882d7b0f40a7fULL, 0x1618f6fc78eb277bULL, 0x6cc0863448deae02ULL,
  0xe3a8176c18803589ULL, 0x997067a428b5bcf0ULL, 0xfa11fe77117cdf02ULL,
  0x80c98ebf2149567bULL, 0x0fa11fe77117cdf0ULL, 0x75796f2f41224489ULL,
  0x3a291b04893d698dULL, 0x40f16bccb908e0f4ULL, 0xcf99fa94e9567b7fULL,
  0xb5418a5cd963f206ULL, 0x513912c379682177ULL, 0x2be1620b495da80eULL,
  0xa489f35319033385ULL, 0xde51839b2936bafcULL, 0x9101f7b0e12997f8ULL,
  0xebd98778d11c1e81ULL, 0x64b116208142850aULL, 0x1e6966e8b1770c73ULL,
  0x8719014c99c2b083ULL, 0xfdc17184a9f739faULL, 0x72a9e0dcf9a9a271ULL,
  0x08719014c99c2b08ULL, 0x4721e43f0183060cULL, 0x3df994f731b68f75ULL,
  0xb29105af61e814feULL, 0xc849756751dd9d87ULL, 0x2c31edf8f1d64ef6ULL,
  0x56e99d30c1e3c78fULL, 0xd9810c6891bd5c04ULL, 0xa3597ca0a188d57dULL,
  0xec09088b6997f879ULL, 0x96d1784359a27100ULL, 0x19b9e91b09fcea8bULL,
  0x636199d339c963f2ULL, 0xdf7adabd7a6e2d6fULL, 0xa5a2aa754a5ba416ULL,
  0x2aca3b2d1a053f9dULL, 0x50124be52a30b6e4ULL, 0x1f423fcee22f9be0ULL,
  0x659a4f06d21a1299ULL, 0xeaf2de5e82448912ULL, 0x902aae96b271006bULL,
  0x74523609127ad31aULL, 0x0e8a46c1224f5a63ULL, 0x81e2d7997211c1e8ULL,
  0xfb3aa75142244891ULL, 0xb46ad37a8a3b6595ULL, 0xceb2a3b2ba0eececULL,
  0x41da32eaea507767ULL, 0x3b024222da65fe1eULL, 0xa2722586f2d042eeULL,
  0xd8aa554ec2e5cb97ULL, 0x57c2c41692bb501cULL, 0x2d1ab4dea28ed965ULL,
  0x624ac0f56a91f461ULL, 0x1892b03d5aa47d18ULL, 0x97fa21650afae693ULL,
  0xed2251ad3acf6feaULL, 0x095ac9329ac4bc9bULL, 0x7382b9faaaf135e2ULL,
  0xfcea28a2faafae69ULL, 0x8632586aca9a2710ULL, 0xc9622c4102850a14ULL,
  0xb3ba5c8932b0836dULL, 0x3cd2cdd162ee18e6ULL, 0x460abd1952db919fULL,
  0x256b24ca6b12f26dULL, 0x5fb354025b277b14ULL, 0xd0dbc55a0b79e09fULL,
  0xaa03b5923b4c69e6ULL, 0xe553c1b9f35344e2ULL, 0x9f8bb171c366cd9bULL,
  0x10e3202993385610ULL, 0x6a3b50e1a30ddf69ULL, 0x8e43c87e03060c18ULL,
  0xf49bb8b633338561ULL, 0x7bf329ee636d1eeaULL, 0x012b592653589793ULL,
  0x4e7b2d0d9b47ba97ULL, 0x34a35dc5ab7233eeULL, 0xbbcbcc9dfb2ca865ULL,
  0xc113bc55cb19211cULL, 0x5863dbf1e3ac9decULL, 0x22bbab39d3991495ULL,
  0xadd33a6183c78f1eULL, 0xd70b4aa9b3f20667ULL, 0x985b3e827bed2b63ULL,
  0xe2834e4a4bd8a21aULL, 0x6debdf121b863991ULL, 0x1733afda2bb3b0e8ULL,
  0xf34b37458bb86399ULL, 0x8993478dbb8deae0ULL, 0x06fbd6d5ebd3716bULL,
  0x7c23a61ddbe6f812ULL, 0x3373d23613f9d516ULL, 0x49aba2fe23cc5c6fULL,
  0xc6c333a67392c7e4ULL, 0xbc1b436e43a74e9dULL, 0x95ac9329ac4bc9b5ULL,
  0xef74e3e19c7e40ccULL, 0x601c72b9cc20db47ULL, 0x1ac40271fc15523eULL,
  0x5594765a340a7f3aULL, 0x2f4c0692043ff643ULL, 0xa02497ca54616dc8ULL,
  0xdafce7026454e4b1ULL, 0x3e847f9dc45f37c0ULL, 0x445c0f55f46abeb9ULL,
  0xcb349e0da4342532ULL, 0xb1eceec59401ac4bULL, 0xfebc9aee5c1e814fULL,
  0x8464ea266c2b0836ULL, 0x0b0c7b7e3c7593bdULL, 0x71d40bb60c401ac4ULL,
  0xe8a46c1224f5a634ULL, 0x927c1cda14c02f4dULL, 0x1d148d82449eb4c6ULL,
  0x67ccfd4a74ab3dbfULL, 0x289c8961bcb410bbULL, 0x5244f9a98c8199c2ULL,
  0xdd2c68f1dcdf0249ULL, 0xa7f41839ecea8b30ULL, 0x438c80a64ce15841ULL,
  0x3954f06e7cd4d138ULL, 0xb63c61362c8a4ab3ULL, 0xcce411fe1cbfc3caULL,
  0x83b465d5d4a0eeceULL, 0xf96c151de49567b7ULL, 0x76048445b4cbfc3cULL,
  0x0cdcf48d84fe7545ULL, 0x6fbd6d5ebd3716b7ULL, 0x15651d968d029fceULL,
  0x9a0d8ccedd5c0445ULL, 0xe0d5fc06ed698d3cULL, 0xaf85882d2576a038ULL,
  0xd55df8e515432941ULL, 0x5a3569bd451db2caULL, 0x20ed197575283bb3ULL,
  0xc49581ead523e8c2ULL, 0xbe4df122e51661bbULL, 0x3125607ab548fa30ULL,
  0x4bfd10b2857d7349ULL, 0x04ad64994d625e4dULL, 0x7e7514517d57d734ULL,
  0xf11d85092d094cbfULL, 0x8bc5f5c11d3cc5c6ULL, 0x12b5926535897936ULL,
  0x686de2ad05bcf04fULL, 0xe70573f555e26bc4ULL, 0x9ddd033d65d7e2bdULL,
  0xd28d7716adc8cfb9ULL, 0xa85507de9dfd46c0ULL, 0x273d9686cda3dd4bULL,
  0x5de5e64efd965432ULL, 0xb99d7ed15d9d8743ULL, 0xc3450e196da80e3aULL,
  0x4c2d9f413df695b1ULL, 0x36f5ef890dc31cc8ULL, 0x79a59ba2c5dc31ccULL,
  0x037deb6af5e9b8b5ULL, 0x8c157a32a5b7233eULL, 0xf6cd0afa9582aa47ULL,
  0x4ad64994d625e4daULL, 0x300e395ce6106da3ULL, 0xbf66a804b64ef628ULL,
  0xc5bed8cc867b7f51ULL, 0x8aeeace74e645255ULL, 0xf036dc2f7e51db2cULL,
  0x7f5e4d772e0f40a7ULL, 0x05863dbf1e3ac9deULL, 0xe1fea520be311aafULL,
  0x9b26d5e88e0493d6ULL, 0x144e44b0de5a085dULL, 0x6e963478ee6f8124ULL,
  0x21c640532670ac20ULL, 0x5b1e309b16452559ULL, 0xd476a1c3461bbed2ULL,
  0xaeaed10b762e37abULL, 0x37deb6af5e9b8b5bULL, 0x4d06c6676eae0222ULL,
  0xc26e573f3ef099a9ULL, 0xb8b627f70ec510d0ULL, 0xf7e653dcc6da3dd4ULL,
  0x8d3e2314f6efb4adULL, 0x0256b24ca6b12f26ULL, 0x788ec2849684a65fULL,
  0x9cf65a1b368f752eULL, 0xe62e2ad306bafc57ULL, 0x6946bb8b56e467dcULL,
  0x139ecb4366d1eea5ULL, 0x5ccebf68aecec3a1ULL, 0x2616cfa09efb4ad8ULL,
  0xa97e5ef8cea5d153ULL, 0xd3a62e30fe90582aULL, 0xb0c7b7e3c7593bd8ULL,
  0xca1fc72bf76cb2a1ULL, 0x45775673a732292aULL, 0x3faf26bb9707a053ULL,
  0x70ff52905f188d57ULL, 0x0a2722586f2d042eULL, 0x854fb3003f739fa5ULL,
  0xff97c3c80f4616dcULL, 0x1bef5b57af4dc5adULL, 0x61372b9f9f784cd4ULL,
  0xee5fbac7cf26d75fULL, 0x9487ca0fff135e26ULL, 0xdbd7be24370c7322ULL,
  0xa10fceec0739fa5bULL, 0x2e675fb4576761d0ULL, 0x54bf2f7c6752e8a9ULL,
  0xcdcf48d84fe75459ULL, 0xb71738107fd2dd20ULL, 0x387fa9482f8c46abULL,
  0x42a7d9801fb9cfd2ULL, 0x0df7adabd7a6e2d6ULL, 0x772fdd63e7936bafULL,
  0xf8474c3bb7cdf024ULL, 0x829f3cf387f8795dULL, 0x66e7a46c27f3aa2cULL,
  0x1c3fd4a417c62355ULL, 0x935745fc4798b8deULL, 0xe98f353477ad31a7ULL,
  0xa6df411fbfb21ca3ULL, 0xdc0731d78f8795daULL, 0x536fa08fdfd90e51ULL,
  0x29b7d047efec8728ULL
};

如何计算有序整数集的哈希值？

2 个答案: