c++ 插入容器元素（insert）

#include <iostream>
#include <vector>
using namespace std;
int main ()
{
    vector<int> myints;
    cout << "0. size: " << myints.size() << '
';
    
    for (int i=0; i<10; i++) myints.push_back(i);
    cout << "1. size: " << myints.size() << '
';
    
    myints.insert (myints.end(),10,100);//起始位置，长度，填充元素
    cout << "2. size: " << myints.size() << '
';
    for (int i=0; i<20; i++) cout << myints[i]<<" ";
    myints.pop_back();
    cout << "
3. size: " << myints.size() << '
';
    
    return 0;
}