public member function
<unordered_set>
size_type count ( const key_type& k ) const;
Count elements with a specific key
Searches the container for elements with a value of k and returns the number of elements found.
Parameters
- k
- Value of the elements to be counted.
Member type key_type is the type of the elements in the container. In unordered_multiset containers it is the same as value_type, defined as an alias of the class's first template parameter (Key).
Return value
The number of elements in the container with a key equivalent to k.
Member type size_type is an unsigned integral type.
Example
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// unordered_multiset::count
#include <iostream>
#include <string>
#include <unordered_set>
int main ()
{
std::unordered_multiset<std::string> myums =
{"cow","pig","chicken","pig","pig","cow"};
for (auto& x: {"cow","sheep","pig"}) {
std::cout << x << ": " << myums.count(x) << std::endl;
}
return 0;
}
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Output:
Complexity
Average case: linear in the number of elements counted.
Worst case: linear in container size.
Iterator validity
No changes.