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C++ multiset empty()C++ Multiset empty() function is used to check whether the multiset container is empty or not. It returns true if the multiset container is empty (size is 0) otherwise, it returns false. Syntaxbool empty() const; // until C++ 11 bool empty const noexcept; //since C++ 11 ParameterNone Return valueThe empty() function returns true if the multiset container is empty (size is 0) otherwise, it returns false. ComplexityConstant. Iterator validityNo changes. Data RacesThe container is accessed. Concurrently accessing the elements of multiset is safe. Exception SafetyThis function never throws exception. Example 1Let's see the simple example to check if a multiset contains any element or not: #include <set> #include <iostream> using namespace std; int main() { multiset<int> numbers; cout << " Initially, numbers.empty(): " << numbers.empty() << "\n"; numbers = {100, 200, 300, 200}; cout << "\n After adding elements, numbers.empty(): " << numbers.empty() << "\n"; } Output: Initially, numbers.empty(): 1 After adding elements, numbers.empty(): 0 In the above example, initially size of multiset is 0 hence, empty() function returns 1 (true) and after adding elements it returns 0 (false). Example 2Let's see a simple example to check whether multiset is empty or not: #include <iostream> #include <set> using namespace std; int main(void) { multiset<char> s; if (s.empty()) cout << "Multiset is empty." << endl; s = {100}; if (!s.empty()) cout << "Multiset is not empty." << endl; return 0; } Output: Multiset is empty Multiset is not empty In the above example, if condition statement is used. If multiset is empty it will return multiset is empty after adding elements it will return multiset is not empty. Example 3Le's see a simple example: #include <iostream> #include <set> using namespace std; int main () { multiset<int> mymultiset; mymultiset = {100, 300, 300, 200, 400, 400}; while (!mymultiset.empty()) { cout << *mymultiset.begin()<< '\n'; mymultiset.erase(*mymultiset.begin()); } return 0; } Output: 100 200 300 400 In the above example, It simply uses the empty() function in while loop and prints the elements of multiset until the multiset is not empty. Example 4Let's see a simple example: #include Output: Multiset is empty. Please insert content! Enter three sets of number: 10002 10002 10003 List of telephone numbers: 10002 10002 10003 In the above example, the program first creates phone multiset interactively with three multiset of numbers. Then it checks if the multiset is empty or not. If multiset is empty, then it displays a message otherwise, it displays all the telephone numbers available in the multiset.
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