C++ Unordered_set Library - size

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Description

It returns the number of elements in the unordered_set container.

Declaration

Following is the declaration for std::unordered_set::size.

C++11

size_type size() const noexcept;

Parameters

none

Return value

It returns the number of elements in the container.

Exceptions

Exception is thrown if any element comparison object throws exception.

Please note that invalid arguments cause undefined behavior.

Time complexity

constant time.

Example

The following example shows the usage of std::unordered_set::size.

#include <iostream>
#include <string>
#include <unordered_set>

int main () {
   std::unordered_set<std::string> myset;
   std::cout << "0. size: " << myset.size() << std::endl;

   myset = {"sairamkrishna","mammahe"};
   std::cout << "1. size: " << myset.size() << std::endl;

   myset.insert ("kittuprasad");
   std::cout << "2. size: " << myset.size() << std::endl;

   myset.erase ("tutorialspoint");
   std::cout << "3. size: " << myset.size() << std::endl;

   return 0;
}

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

0. size: 0
1. size: 2
2. size: 3
3. size: 3