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unordered_map get_allocator in C++ STL

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  • Last Updated : 19 Dec, 2018
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unordered_map::get_allocator() is a built in function in C++ STL which is used to get allocator of container unordered_map.
Syntax

Allocator_type get_allocator()

Parameters: This function does not accept any parameter.
Return value: Returns an allocator associated with unordered_map.

Below programs explains clearly the unordered_map::get_allocator() function.
Example-1:




// CPP program to illustrate
// unordered_map get_allocator()
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
  
    //'ump' is object of 'unordered_ump'
    unordered_map<int, int> ump;
  
    //'allocator_type' is inherit in 'unordered_map'
    //'u' is object of 'allocator_type'
    unordered_map<int, int>::allocator_type u = ump.get_allocator();
  
    // Comparing the Allocator with Pair<int, int>
    cout << "Is allocator Pair<int, int> : "
         << boolalpha
         << (u == allocator<pair<int, int> >());
  
    return 0;
}


Output:

Is allocator Pair : true

Example-2:




// CPP program to illustrate
// unordered_map get_allocator()
#include <bits/stdc++.h>
using namespace std;
  
int main(void)
{
    unordered_map<char, int> um;
    pair<const char, int>* a;
  
    a = um.get_allocator().allocate(8);
  
    cout << "Allocated size = " << sizeof(*a) * 8 << endl;
  
    return 0;
}


Output:

Allocated size = 64

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