auto keyword demo

#include <iostream>#include <vector>using namespace std;int main(){    int v1 = 10;    int v2 = 20;    auto v = v1 + v2;    cout << v << endl;    vector<int> ivec { 1, 2, 3, 4 };    for (auto elem : ivec)        cout << elem << " ";    cout << endl;    for (auto it = ivec.begin(); it != ivec.end(); ++it)        cout << *it << " ";    cout << endl;    return 0;}