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The user defined function can be used as is in std::unordered_map, by passing it as a template parameter std :: unordered_map < X , int , hash_X > my_map ; Or can be set as the default hash function by specializing the std::hash function
Function object binders (bind) – can bind any parameter parameters to function objects. Function composition is also allowed. This is a generalized version of the standard std::bind1st and std::bind2nd bind functions. The feature is based on Boost Bind library. [4] Function return types (result_of) – determines the type of a call expression.
A hash table uses a hash function to compute an index, also called a hash code, into an array of buckets or slots, from which the desired value can be found. During lookup, the key is hashed and the resulting hash indicates where the corresponding value is stored. A map implemented by a hash table is called a hash map.
The same must be true for all of the values. Although std::map is typically implemented using a self-balancing binary search tree, C++11 defines a second map called std::unordered_map, which has the algorithmic characteristics of a hash table.
The C++ Standard Library provides several generic containers, functions to use and manipulate these containers, function objects, generic strings and streams (including interactive and file I/O), support for some language features, and functions for common tasks such as finding the square root of a number.
Type of key must implement comparison operator < or custom comparator function must be specified; such comparison operator or comparator function must guarantee strict weak ordering, otherwise behavior is undefined. Typically implemented using a self-balancing binary search tree. multimap same as a map, but allows duplicate keys. hash_set hash ...
A concurrent hash table or concurrent hash map is an implementation of hash tables allowing concurrent access by multiple threads using a hash function. [ 1 ] [ 2 ] Concurrent hash tables represent a key concurrent data structure for use in concurrent computing which allow multiple threads to more efficiently cooperate for a computation among ...
Example shown above demonstrates the usage of some of the functions provided by map, such as insert() (place element into the map), erase() (remove element from the map), find() (check presence of the element in the container), etc.