The C++ function std::unordered_multimap::hash_function() calculates the hash function object used by the unordered_multimap container.
The hash function is a unary function that takes an object of type key_type as argument and returns a unique value of type size_t based on it.
Following is the declaration for std::unordered_multimap::hash_function() function form std::unordered_map() header.
hasher hash_function() const;
None
Returns the hash function.
Constant i.e. O(1)
The following example shows the usage of std::unordered_multimap::hash_function() function.
#include <iostream> #include <unordered_map> using namespace std; int main(void) { unordered_multimap <string, string> umm; auto fun = umm.hash_function(); cout << "Hash function for a = " << fun("a") << endl; cout << "Hash function for A = " << fun("A") << endl; return 0; }
Let us compile and run the above program, this will produce the following result −
Hash function for a = 4993892634952068459 Hash function for A = 6919333181322027406