数组、模板类vector对象、模板类array对象

#include <iostream>#include <vector>#include <array>int main(){using namespace std;double a1[4]={1.2,2.4,3.6,4.8};vector<double> a2(4);a2[0]=1.0/3.0;a2[1]=1.0/5.0;a2[2]=1.0/7.0;a2[3]=1.0/9.0;array<double,4> a3={3.14,2.72,1.62,1.41};array<double,4> a4;a4=a3;cout<<" a1[2]: "<<a1[2]<<" at "<<&a1[2]<<endl;cout<<" a2[2]: "<<a2[2]<<" at "<<&a2[2]<<endl;cout<<" a3[2]: "<<a3[2]<<" at "<<&a3[2]<<endl;cout<<" a4[2]: "<<a4[2]<<" at "<<&a4[2]<<endl;a1[-2]=20.2;cout<<" a1[-2]: "<<a1[-2]<<" at "<<&a2[-2]<<endl;cout<<" a3[2]: "<<a3[2]<<" at "<<&a3[2]<<endl;cout<<" a4[2]: "<<a4[2]<<" at "<<&a4[2]<<endl;return 0;}//a1[-2]=20.2; 找到a1位置 前移两个单位 是不安全的代码