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  2. Unordered associative containers (C++) - Wikipedia

    en.wikipedia.org/wiki/Unordered_associative...

    To use custom objects in std::unordered_map, a custom hash function must be defined. This function takes a const reference to the custom type and returns a size_t #include <unordered_map> struct X { int i , j , k ;}; struct hash_X { size_t operator ()( const X & x ) const { return std :: hash < int > ()( x . i ) ^ std :: hash < int > ()( x . j ...

  3. Hash function - Wikipedia

    en.wikipedia.org/wiki/Hash_function

    A hash function is any function that can be used to map data of arbitrary size to fixed-size values, though there are some hash functions that support variable-length output. [1] The values returned by a hash function are called hash values , hash codes , hash digests , digests , or simply hashes . [ 2 ]

  4. Perfect hash function - Wikipedia

    en.wikipedia.org/wiki/Perfect_hash_function

    A perfect hash function can, as any hash function, be used to implement hash tables, with the advantage that no collision resolution has to be implemented. In addition, if the keys are not in the data and if it is known that queried keys will be valid, then the keys do not need to be stored in the lookup table, saving space.

  5. MurmurHash - Wikipedia

    en.wikipedia.org/wiki/MurmurHash

    MurmurHash is a non-cryptographic hash function suitable for general hash-based lookup. [1] [2] [3] It was created by Austin Appleby in 2008 [4] and, as of 8 January 2016, [5] is hosted on GitHub along with its test suite named SMHasher. It also exists in a number of variants, [6] all of which have been released into the public domain. The name ...

  6. Hash table - Wikipedia

    en.wikipedia.org/wiki/Hash_table

    A small phone book as a hash table. In computer science, a hash table is a data structure that implements an associative array, also called a dictionary or simply map; an associative array is an abstract data type that maps keys to values. [2]

  7. List of hash functions - Wikipedia

    en.wikipedia.org/wiki/List_of_hash_functions

    hash JH: 224 to 512 bits hash LSH [19] 256 to 512 bits wide-pipe Merkle–Damgård construction: MD2: 128 bits hash MD4: 128 bits hash MD5: 128 bits Merkle–Damgård construction: MD6: up to 512 bits Merkle tree NLFSR (it is also a keyed hash function) RadioGatún: arbitrary ideal mangling function RIPEMD: 128 bits hash RIPEMD-128: 128 bits ...

  8. Virtual method table - Wikipedia

    en.wikipedia.org/wiki/Virtual_method_table

    When an object is created, a pointer to this table, called the virtual table pointer, vpointer or VPTR, is added as a hidden member of this object. As such, the compiler must also generate "hidden" code in the constructors of each class to initialize a new object's virtual table pointer to the address of its class's virtual method table.

  9. Pearson hashing - Wikipedia

    en.wikipedia.org/wiki/Pearson_hashing

    This hash function is a CBC-MAC that uses an 8-bit substitution cipher implemented via the substitution table. An 8-bit cipher has negligible cryptographic security, so the Pearson hash function is not cryptographically strong , but it is useful for implementing hash tables or as a data integrity check code , for which purposes it offers these ...