#include <iostream>
#include <vector>

//STL组件属于std名称空间，以下不再赘述
using namespace std ;

int main(){
    cout << "enter the number of element:" << endl ;
    int num ;
    cin >> num ;
    if ( num == 0 ){
        cout << "please enter again" << endl ;
        cin >> num ;
    }

    //定义一个数据类型为 int 的 vector 容器 vec
    vector<int> vec ;
    for ( int i = 0 ; i < num ; i ++ ){
        cout << "input: " ;
        int number ;
        cin >> number ;
        //将元素添加至表尾
        vec.push_back(number) ;
    }

    //定义一个正向迭代器 it
    vector<int>::iterator it ;
    //定义一个反向迭代器 rit
    vector<int>::reverse_iterator rit ;
    cout << endl << "output:" << endl ;
    //正向输出
    cout << "in order: " << endl ;
    for ( it = vec.begin() ; it != vec.end() ; it ++ ){
        cout << *it << " " ;
    }
    cout << endl ;
    //反向输出
    cout << "reverse order: " << endl ;
    for ( rit = vec.rbegin() ; rit != vec.rend() ; rit ++ ){
        cout << *rit << " " ;
    }
    cout << endl << endl ;

    //插入操作
    cout << "insert:(position , element)" << endl ;
    int pos , element ;
    cin >> pos >> element ;
    if ( pos < 0 || pos > vec.size() ){
        cout << "please enter position again" << endl ;
        cin >> pos ;
    }
    vec.insert(vec.begin() + pos , element) ;
    cout << "there are *" << vec.size() << "* numbers now" << endl ;
    cout << "output:" << endl ;
    for ( it = vec.begin() ; it != vec.end() ; it ++ ){
        cout << *it << " " ;
    }
    cout << endl << endl ;

    //删除操作
    cout << "erase:(begin , end)" << endl ;
    int first , last ;
    cin >> first >> last ;
    if ( first < 0 || last > vec.size() ){
        cout << "please enter again" << endl ;
        cin >> first >> last ;
    }
    vec.erase(vec.begin() + first , vec.begin() + last) ;
    if ( !vec.empty() ){
        cout << "there are *" << vec.size() << "* numbers now" << endl ;
        for ( it = vec.begin() ; it != vec.end() ; it ++ ){
            cout << *it << " " ;
        }
    }else{
        cout << "the vector is empty now!" << endl ;
    }
    cout << endl ;
    return 0 ;
}