C++ Unordered_map Library - max_size() Function

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Description

The C++ function std::unordered_map::max_size() returns the maximum number of elements can be held by unordered_map.

This value depends on system or library implementation.

Declaration

Following is the declaration for std::unordered_map::max_size() function form std::unordered_map header.

C++11

size_type max_size() const noexcept;

Parameters

None

Return value

returns the maximum number of elements can be held by unordered_map.

Exceptions

This member function never throws exception.

Time complexity

Constant i.e. O(1)

Example

The following example shows the usage of std::unordered_map::max_size() function.

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void) {
   unordered_map<char, int> um;

   cout << "max_size of unordered_map = " << um.max_size() << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

max_size of unordered_map = 1152921504606846975