Size

For a container cont, you can check with cont.empty() if the container is empty. cont.size() returns the current number of elements, and cont.max_size() returns the maximum number of elements cont can have. The maximum number of elements is implementation defined.

Size of a container

// containerSize.cpp 
...
#include <map>
#include <set>
#include <vector>
...
using namespace std;

vector<int> intVec{1, 2, 3, 4, 5, 6, 7, 8, 9};
map<string, int> str2Int = {{"bart", 12345}, 
                            {"jenne", 34929}, {"huber", 840284}};
set<double> douSet{3.14, 2.5};

cout << intVec.empty() << endl;  // false
cout << str2Int.empty() << endl; // false
cout << douSet.empty() << endl;  // false

cout << intVec.size() << endl;  // 9
cout << str2Int.size() << endl; // 3
cout << douSet.size() << endl;  // 2

cout << intVec.max_size() &lt...