public member function

std::set::count

<set>
size_type count ( const key_type& x ) const;
Count elements with a specific key
Searches the container for an element with a key of x and returns the number of times the element appears in the container. Because set containers do not allow for duplicate keys, this means that the function actually returns 1 if the element is found, and zero otherwise.

Parameters

x
Value to be searched for.
key_type is a member type defined in set containers as an alias of Key, which is the first template parameter and the type of the elements stored in the container.

Return value

1 if an element with a key equivalent to x is found, or zero otherwise.

Member type size_type is an unsigned integral type.

Example

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// set::count
#include <iostream>
#include <set>
using namespace std;

int main ()
{
  set<int> myset;
  int i;

  // set some initial values:
  for (i=1; i<5; i++) myset.insert(i*3);    // set: 3 6 9 12

  for (i=0;i<10; i++)
  {
    cout << i;
    if (myset.count(i)>0)
      cout << " is an element of myset.\n";
    else 
      cout << " is not an element of myset.\n";
  }

  return 0;
}


Output:
0 is not an element of myset.
1 is not an element of myset.
2 is not an element of myset.
3 is an element of myset.
4 is not an element of myset.
5 is not an element of myset.
6 is an element of myset.
7 is not an element of myset.
8 is not an element of myset.
9 is an element of myset.

Complexity

Logarithmic in size.

See also

set::find
Get iterator to element (public member function)
set::size
Return container size (public member function)
set::lower_bound
Return iterator to lower bound (public member function)
set::upper_bound
Return iterator to upper bound (public member function)