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C++ Unordered_map Library - hash_function() Function
Description
The C++ function std::unordered_map::hash_function() Calculates the hash function object used by the unordered_map 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.
Declaration
Following is the declaration for std::unordered_map::hash_function() function form std::unordered_map header.
C++11
hasher hash_function() const;
Parameters
None
Return value
Returns the hash function.
Time complexity
Constant i.e. O(1)
Example
The following example shows the usage of std::unordered_map::hash_function() function.
#include <iostream> #include <unordered_map> using namespace std; int main(void) { unordered_map <string, string> um; auto fun = um.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
unordered_map.htm
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