set::count
public member function
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;
}
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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.
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Complexity
Logarithmic in size.
See also
| set::find | Get iterator to element (public member function) |
| set::size | Return container size (public member function) |
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