C++ multiset count
The count function in C++ Multiset is employed to determine the quantity of elements existing within the container. As the multiset container prohibits duplicate elements, this function returns 1 when the element with the specified value val is present in the multiset container; otherwise, it returns 0.
Syntax
size_type count (const value_type& val) const;
Parameter
val : The value to be searched within the multiset container.
Return value
It returns 1 if the element containing the specified value val exists within the multiset container, otherwise it returns 0.
Complexity
Logarithmic in size.
Iterator validity
No changes.
Data Races
The container is accessed.
Simultaneously retrieving the elements of a container is considered to be a secure operation.
Exception Safety
If an error is triggered, the multiset remains unchanged.
Example 1
Let's explore a basic example of searching for an element based on a specified key value:
#include <iostream>
#include <set>
using namespace std;
int main()
{
// initialize container
multiset<int> mp;
// insert elements in random order
mp.insert( 30 );
mp.insert( 40 );
mp.insert( 30 );
mp.insert( 20);
mp.insert( 50 );
// checks if key 30 is present or not
if (mp.count(30))
cout << "The key 30 is present\n";
else
cout << "The key 30 is not present\n";
// checks if key 100 is present or not
if (mp.count(100))
cout << "The key 100 is present\n";
else
cout << "The key 100 is not present\n";
return 0;
}
Output:
The key 30 is present
The key 100 is not present
In the example provided, the count method verifies the presence of a specified value. If the element exists within the multiset container, a message indicating its presence is shown; otherwise, it indicates that the element is not found.
Example 2
Let's examine a basic example of searching for elements within a multiset:
#include <iostream>
#include <set>
using namespace std;
int main ()
{
multiset<char> mymultiset;
char c;
mymultiset = {'a', 'c', 'f'};
for (c='a'; c<'h'; c++)
{
cout << c;
if (mymultiset.count(c)>0)
cout << " is an element of mymultiset.\n";
else
cout << " is not an element of mymultiset.\n";
}
return 0;
}
Output:
a is an element of mymultiset.
b is not an element of mymultiset.
c is an element of mymultiset.
d is not an element of mymultiset.
e is not an element of mymultiset.
f is an element of mymultiset.
g is not an element of mymultiset.
In the given illustration, the count method is employed to locate the elements 'a' through 'h' within the multiset.
Example 3
Let's explore a basic example of searching for keys within a multiset:
#include <iostream>
#include <set>
using namespace std;
int main(void) {
multiset<char> m = {'a','b','b','d'};
if (m.count('a') == 1) {
cout<< " 'a' is present in the multiset \n";
}
if (m.count('z') == 0) {
cout << " 'z' is not present in the multiset" << endl;
}
return 0;
}
Output:
'a' is present in the multiset
'z' is not present in the multiset
In the previous illustration, the element 'a' is found in the multiset m, so it will be the assigned value for 'a'. Conversely, the element 'z' is absent in the multiset, resulting in no assigned value for 'z'.
Example 4
Let's see a simple example:
#include <set>
#include <iostream>
int main()
{
using namespace std;
multiset<int> s1;
multiset<int>::size_type i;
s1.insert(1);
s1.insert(1);
// Keys must be unique in multiset, so duplicates are ignored
i = s1.count(1);
cout << "The number of elements in s1 with a sort key of 1 is: "
<< i << "." << endl;
i = s1.count(2);
cout << "The number of elements in s1 with a sort key of 2 is: "
<< i << "." << endl;
}
Output:
The number of elements in s1 with a sort key of 1 is: 1.
The number of elements in s1 with a sort key of 2 is: 0.
