unordered_map size() in C++ STL (original) (raw)

Last Updated : 12 Apr, 2023

The unordered_multimap::size() is a built-in function in C++ Standard Template Library which return's the number of element in the unordered map. Syntax:

unordered_multimap_name.size()

Return Value: It returns the number of the element present in the unordered map. Time complexity:

Constant i.e. O(1).

Program 1:

CPP `

// C++ program to demonstrate // unordered_map size() method

#include #include using namespace std;

int main() { unordered_map<char, char> n{ { 'A', 'G' }, { 'B', 'E' }, { 'C', 'E' }, { 'D', 'K' }, { 'E', 'S' } };

cout << "size of map = "
     << n.size() << endl;

return 0;

}

`

Program 2:

CPP `

// C++ program to demonstrate // unordered_map size() method

#include #include #include using namespace std;

int main() { unordered_map<string, double> ra;

cout << "Initial size of map = "
     << ra.size() << endl;

ra = {
    { "Geeks", 1.556 },
    { "For", 2.567 },
    { "Geeks", 3.345 },
    { "GeeksForGeeks", 4.789 },
    { "GFG", 5.998 }
};

cout << "size of map = "
     << ra.size() << endl;

return 0;

}

`

Output:

Initial size of map = 0 size of map = 4