C++ Set Library - count Function

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Description

It searches the container for elements equivalent to val and returns the number of matches.

Declaration

Following are the ways in which std::set::count works in various C++ versions.

C++98

size_type count (const value_type& val) const;

C++11

size_type count (const value_type& val) const;

Return value

It returns the number of matche

Exceptions

If an exception is thrown, there are no changes in the container.

Time complexity

Time complexity depens on logarithmic.

Example

The following example shows the usage of std::set::count.

#include <iostream>
#include <set>

int main () {
   std::set<int> myset;

   for (int i = 1; i < 15;++i) myset.insert(i*5);

   for (int i = 0; i < 5; ++i) {
      std::cout << i;
      if (myset.count(i)!=0)
         std::cout << " is an element of myset.\n";
      else
         std::cout << " is not an element of myset.\n";
   }

   return 0;
}

The above program will compile and execute properly.

0 is not an element of myset.
1 is not an element of myset.
2 is not an element of myset.
3 is not an element of myset.
4 is not an element of myset.