c++ 判断容器是否为空

#include <iostream>
#include <vector>
#include <string>
using namespace std;
int main()
{
    vector<int> ints {, , };
    vector<string> fruits {"orange", "apple", "raspberry"};
    vector<char> empty;

    // Sums all integers in the vector ints (if any), printing only the result.
    int sum = ;
    for (auto it = ints.cbegin(); it != ints.cend(); it++)
        sum += *it;
    cout << "Sum of ints: " << sum << "\n";

    // 输出容器的第一个元素
    cout << "First fruit: " << *fruits.begin() << "\n";

    if (empty.begin() == empty.end())
        cout << "vector 'empty' is indeed empty.\n";
}