get_allocator() in C++ Last Updated : 01 Jun, 2018 Comments Improve Suggest changes Like Article Like Report In STL, containers can change size dynamically. Allocator is an object that is responsible for dynamic memory allocation/deallocation. get_allocator() is used to allocate memory chunks of memory. It returns a copy of the allocator object associated with the container. It is defined in vector, map, list, set libraries. Syntax: allocator_type get_allocator() const; Parameter Used: This member function does not need any parameter to be passed. Return Type: It returns a copy of the allocator object associated with the vector. Errors and Exceptions: Never throws exceptions so we don't need any try-catch surrounding of it. Time-Complexity: Constant O(1). Below programs illustrate the working of the function 1. std::vector::get_allocator() It returns a copy of the allocator object associated with the vector. CPP // C++ program to show working // of get_allocator function #include <iostream> #include <vector> using namespace std; // Function for allocating char* Allocate(vector<char> arr, int size) { // allocate space for size(s) elements return arr.get_allocator().allocate(size); } void Construct(vector<char> arr, char* point, int size) { for (int iter = 0; iter < size; ++iter) // construct values in-place on the array: arr.get_allocator().construct(&point[iter], iter + 97); } // Function for Deallocating void deAllocate(vector<char> arr, char* point, int size) { for (int iter = 0; iter < size; ++iter) arr.get_allocator().destroy(&point[iter]); // free allocated memory arr.get_allocator().deallocate(point, size); } // Driver code int main() { vector<char> array; char* pointer; int size = 8; pointer = Allocate(array, size); Construct(array, pointer, size); cout << "Array elements: "; for (int iter = 0; iter < size; ++iter) cout << pointer[iter] << " "; deAllocate(array, pointer, size); return 0; } Output: Array elements: a b c d e f g h 2. std::list::get_allocator() It returns a copy of the allocator object associated with the list. CPP // C++ program to show working // of get_allocator function #include <iostream> #include <list> using namespace std; // Function for allocating char* Allocate(list<char> arr, int size) { // allocate space for size(s) elements return arr.get_allocator().allocate(size); } void Construct(list<char> arr, char* point, int size) { for (int iter = 0; iter < size; ++iter) // construct values in-place on the array: arr.get_allocator().construct(&point[iter], iter + 97); } // Function for Deallocating void deAllocate(list<char> arr, char* point, int size) { for (int iter = 0; iter < size; ++iter) arr.get_allocator().destroy(&point[iter]); // free allocated memory arr.get_allocator().deallocate(point, size); } // Driver code int main() { list<char> array; char* pointer; int size = 8; pointer = Allocate(array, size); Construct(array, pointer, size); cout << "Array elements: "; for (int iter = 0; iter < size; ++iter) cout << pointer[iter] << " "; deAllocate(array, pointer, size); return 0; } Output: Array elements: a b c d e f g h 3. std::set::get_allocator() It returns a copy of the allocator object associated with the set. CPP // C++ program to show working // of get_allocator function #include <iostream> #include <set> using namespace std; // Function for allocating char* Allocate(set<char> arr, int size) { // allocate space for size(s) elements return arr.get_allocator().allocate(size); } void Construct(set<char> arr, char* point, int size) { for (int iter = 0; iter < size; ++iter) // construct values in-place on the array: arr.get_allocator().construct(&point[iter], iter + 97); } // Function for Deallocating void deAllocate(set<char> arr, char* point, int size) { for (int iter = 0; iter < size; ++iter) arr.get_allocator().destroy(&point[iter]); // free allocated memory arr.get_allocator().deallocate(point, size); } // Driver code int main() { set<char> array; char* pointer; int size = 8; pointer = Allocate(array, size); Construct(array, pointer, size); cout << "Array elements: "; for (int iter = 0; iter < size; ++iter) cout << pointer[iter] << " "; deAllocate(array, pointer, size); return 0; } Output: Array elements: a b c d e f g h References: http://www.cplusplus.com/reference/vector/vector/get_allocator/ Comment More infoAdvertise with us Next Article get_allocator() in C++ D Dibyendu Roy Chaudhuri Follow Improve Article Tags : C++ DSA STL cpp-containers-library Practice Tags : CPPSTL Similar Reads DSA Tutorial - Learn Data Structures and Algorithms DSA (Data Structures and Algorithms) is the study of organizing data efficiently using data structures like arrays, stacks, and trees, paired with step-by-step procedures (or algorithms) to solve problems effectively. 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