[C] Modifying a vector in-place

#include <vector>
#include <iostream>

using std::vector;
using std::cout;
using std::endl;

int main() {
    vector<int> vec {1, 2, 3};

    // Modify vec in-place!
    for (auto ptr = vec.begin(); ptr != vec.end(); ptr++) {
        *ptr = (*ptr) * (*ptr);
    }

    // Print out the data of vec in console
    for (auto ptr = vec.begin(); ptr != vec.end(); ptr++) {
        cout << *ptr << " ";
    }
    cout << endl;

    return 0;
}