//编写程序获取vector容器的第一个元素，分别使用下标操作符，front函数以及begin函数实现该功能，并提供空的vector容器测试你的程序
#include<iostream>
#include<vector>
using namespace std;
int main(void)
{
    cout<<"\tInput some int numbers to a vector(Ctrl+Z to end):"<<endl;
    vector<int> ivec;
    int i;
    while(cin>>i)
    {
        ivec.push_back(i);
    }
    if(!ivec.empty())
    {
        cout<<"The first elements of the vector is:";
        cout<<"\n\t==>>Using front():\t"<<ivec.front();
        cout<<"\n\t==>>Using begin():\t"<<ivec.begin();
        cout<<"\n\t==>>Using ivec[0]:\t"<<ivec[0];
        cout<<"\n\t==>>Using ivec.at(0):\t"<<ivec.at(0)<<endl;
    }
    system("pause");
    return 0;
}

#include<iostream>
#include<vector>
using namespace std;
int main(void)
{
    cout << "\tInput some int numbers to a vector(Ctrl+Z to end):" << endl;
    vector<int> ivec;
    int i;
    while (cin >> i)
    {
        ivec.push_back(i);
    }
    if (!ivec.empty())
    {
        cout << "The first elements of the vector is:";
        cout << "\n\t==>>Using front():\t" << ivec.front();
        cout << "\n\t==>>Using begin():\t" << *(ivec.begin());
        cout << "\n\t==>>Using ivec[0]:\t" << ivec[0];
        cout << "\n\t==>>Using ivec.at(0):\t" << ivec.at(0) << endl;
    }
    system("pause");
    return 0;
}