unordered_map count() in C++ (original) (raw)

Last Updated : 26 Sep, 2018

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:

CPP `

// C++ program to illustrate the // unordered_map::count() function

#include #include

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;

}

`

Program 2:

CPP `

// C++ program to illustrate the // unordered_map::count() function

#include #include

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;

}

`

Output:

Count of elements in map, mapped with key 3: 1