$ g++ --version
g++ (Homebrew GCC 9.2.0) 9.2.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> v { 20, 30, 50 };
     v.push_back(90);
     v[0] = 1;

    for (int v2: v) {
        printf("%d\n", v2);
    }

    printf("---\n");

    for (vector<int>::iterator it = v.begin(); it != v.end(); it++) {
        printf("%d\n", *it);
    }
}

1
30
50
90
---
1
30
50
90