The unordered_set::size() method is a builtin function in C++ STL which is used to return the number of elements in the unordered_set container.
Syntax:
unordered_set_name.size()
Parameter: It does not accepts any parameter.
Return Value: The function returns the number of elements in the container. Below programs illustrate the unordered_set::size() function:
Program 1:
CPP
// C++ program to illustrate the // unordered_set.size() function #include <iostream> #include <unordered_set> using namespace std;
int main()
{ unordered_set< int > arr1 = { 1, 2, 3, 4, 5 };
// prints the size of arr1
cout << "size of arr1:" << arr1.size();
// prints the element
cout << "\nThe elements are: " ;
for ( auto it = arr1.begin(); it != arr1.end(); it++)
cout << *it << " " ;
return 0;
} |
Output:
size of arr1:5 The elements are: 5 1 2 3 4
Program 2:
CPP
// C++ program to illustrate the // unordered_set::size() function // when container is empty #include <iostream> #include <unordered_set> using namespace std;
int main()
{ unordered_set< int > arr2 = {};
// prints the size
cout << "Size of arr2 : " << arr2.size();
return 0;
} |
Output:
Size of arr2 : 0
Time complexity: O(1)