3.41

#include<iostream>
#include <vector>
using namespace std;


int main() {
    int a1[] = { 1,2,3,4,5 };
    vector<int> a2(begin(a1), end(a1));
    for(auto i:a2)
    cout << i << endl;  

        return 0;
}

3.42

#include<iostream>
#include <vector>
using namespace std;


int main() {
    vector<int> a2{ 1,2,3,4,5 };
    int a1[5];
    for (size_t i = 0;i != a2.size();++i) {  //嗯,这里个题目就是size_t的使用
        a1[i] = a2[i];
    }
    for(auto e:a1)
        cout << e << endl;


        return 0;
}