The unordered_map::count() is a builtin method in C++ which is used to count the number of elements present in an unordered_map with a given key.
Note: As unordered_map does not allow to store elements with duplicate keys, so the count() function basically checks if there exists an element in the unordered_map with a given key or not.
Syntax:
size_type count(Key);
Parameters: This function accepts a single parameter key which is needed to be checked in the given unordered_map container.
Return Value: This function returns 1 if there exists a value in the map with the given key, otherwise it returns 0.
Below programs illustrate the unordered_map::count() function:
Program 1:
// C++ program to illustrate the // unordered_map::count() function #include<iostream> #include<unordered_map> using namespace std;
int main()
{ // unordered map
unordered_map< int , string> umap;
// Inserting elements into the map
umap.insert(make_pair(1, "Welcome" ));
umap.insert(make_pair(2, "to" ));
umap.insert(make_pair(3, "GeeksforGeeks" ));
// Check if element with key 1 is present using
// count() function
if (umap.count(1))
{
cout<< "Element Found" <<endl;
}
else
{
cout<< "Element Not Found" <<endl;
}
return 0;
} |
Element Found
Program 2:
// C++ program to illustrate the // unordered_map::count() function #include<iostream> #include<unordered_map> using namespace std;
int main()
{ // unordered map
unordered_map< int , string> umap;
// Inserting elements into the map
umap.insert(make_pair(1, "Welcome" ));
umap.insert(make_pair(2, "to" ));
umap.insert(make_pair(3, "GeeksforGeeks" ));
// Try inserting element with
// duplicate keys
umap.insert(make_pair(3, "CS Portal" ));
// Print the count of values with key 3
// to check if duplicate values are stored
// or not
cout<< "Count of elements in map, mapped with key 3: "
<<umap.count(3);
return 0;
} |
Count of elements in map, mapped with key 3: 1